The VELUX skylight size chart has 14 deck-mounted codes (A06 through S06), 10 venting curb-mounted codes (2222 through 4646), 18 standard fixed curb codes, and three Sun Tunnel diameters (10, 14 and 22 inches). Deck-mounted codes run from a 14 1/2 x 45 3/4 inch rough opening (A06) to 44 1/4 x 45 3/4 inches (S06), per VELUX’s March 2026 Skylight Measurement Guide. The letter in a deck code sets the width, the number sets the height, and a curb code simply states the inside curb in inches. Every figure below comes from VELUX America’s own published size charts and product pages; where VELUX does not publish a size, it is left out.
By The Roofing Brief Team ยท Last reviewed: October 2026
Key VELUX size numbers at a glance
These are the figures most people search a VELUX skylight size chart for: how many sizes exist, the smallest and largest openings, and the roof pitch each family accepts. All values are VELUX America published specifications as of 2026 and may change, so confirm against the current VELUX price list or customer service (800-888-3589) before ordering.
| What you need to know | VELUX figure | Source |
|---|---|---|
| Deck-mounted sizes (FS, VS, VSE, VSS) | 14 codes; rough opening 14 1/2 x 45 3/4 in (A06) to 44 1/4 x 45 3/4 in (S06); tallest is C12 at 21 x 70 1/4 in | VELUX Skylight Measurement Guide (v-5859, 2026) |
| Venting curb-mounted sizes (VCS, VCE, VCM) | 10 codes for solar VCS; 7 for electric VCE and manual VCM; inside curb 22 1/2 x 22 1/2 in (2222) to 46 1/2 x 46 1/2 in (4646) | VELUX USA Skylight Size Guide |
| Fixed curb-mounted sizes (FCM) | 18 standard codes, 1943 to 4672 (outside curb up to 49 1/2 x 75 1/2 in), plus custom sizes | VELUX USA Skylight Size Guide |
| Sun Tunnel diameters | 10, 14 and 22 in; rigid kits include 4 ft of tube, flexible kits 8 ft | VELUX pro product pages (TGR, TMR, TGF) |
| Roof pitch range | Deck-mounted 14 to 85 degrees (3:12 to 137:12); curb-mounted 0 to 60 degrees (0:12 to 20:12); Sun Tunnel 14 to 60 degrees | VELUX Skylight Measurement Guide; VELUX Sun Tunnel pages |
How do you read a VELUX skylight size code?
A VELUX deck-mounted size code is a letter plus two digits: the letter fixes the width (A, C, D, M or S) and the digits fix the height (01, 02, 04, 06, 08, 12 or 26). A curb-mounted code is four digits that state the inside curb width and height in whole inches, so 2246 means a 22 1/2 x 46 1/2 inch inside curb. The two systems are not interchangeable: a C06 and a 2246 are different products for different roof details.
The width letters and height numbers map to these deck-mounted rough openings. Read across the letter row and down the number row, then confirm the exact pair exists in the full chart, because VELUX does not make every combination (there is no A01 or S08, for example).
| Code part | Means | Rough opening dimension | Source |
|---|---|---|---|
| A | Narrowest width | 14 1/2 in wide | VELUX 2026 guide |
| C | Standard narrow width | 21 in wide | VELUX 2026 guide |
| D | Truss-bay width | 22 1/2 in wide | VELUX 2026 guide |
| M | Standard wide width | 30 1/16 in wide | VELUX 2026 guide |
| S | Widest | 44 1/4 in wide | VELUX 2026 guide |
| 01 / 02 / 04 | Short heights | 26 7/8 / 30 / 37 7/8 in high | VELUX 2026 guide |
| 06 / 08 / 12 | Mid to tall heights | 45 3/4 / 54 7/16 / 70 1/4 in high | VELUX 2026 guide |
| 26 | Near-square compact (D26 only) | 22 15/16 in high | VELUX 2026 guide |
The size code sits inside a longer ordering code. VELUX’s own example, FS C06 2004S, reads as model FS (fixed, deck-mounted), size C06, interior finish 2 (white), cladding 0 (aluminum), glazing 04 (laminated LowE3), and S for the white room-darkening solar shade that VELUX now ships as standard on its skylight systems. Older units carry three-digit sizes instead: 106 is today’s C06 and 306 is today’s M06, as shown in the crosswalk column of the deck chart below.
VELUX deck-mounted skylight size chart (FS, VS, VSE, VSS)
Deck-mounted VELUX skylights mount directly to the roof deck with a VELUX flashing kit, and the same size code gives the same rough opening whether the unit is fixed (FS), manual venting (VS), electric venting (VSE) or solar venting (VSS). The fixed FS comes in all 14 sizes; the venting models come in 10, and the electric VSE skips M02. Frame to the rough opening column, not the outside frame.
| Size code (old code) | Rough opening W x H (in) | Outside frame W x H (in) | Finished drywall W x H (in) | Fits rafters on center | Daylight area fixed / venting (sq ft) | Models offered |
|---|---|---|---|---|---|---|
| A06 (056) | 14 1/2 x 45 3/4 | 15 1/4 x 46 1/4 | 13 1/4 x 44 1/4 | 16 in | 2.76 / not offered | FS only |
| C01 (101) | 21 x 26 7/8 | 21 1/2 x 27 3/8 | 19 1/2 x 25 3/8 | 24 in | 2.40 / 1.76 | FS, VS, VSE, VSS |
| C04 (104) | 21 x 37 7/8 | 21 1/2 x 38 3/8 | 19 1/2 x 36 3/8 | 24 in | 3.67 / 2.86 | FS, VS, VSE, VSS |
| C06 (106) | 21 x 45 3/4 | 21 1/2 x 46 1/4 | 19 1/2 x 44 1/4 | 24 in | 4.56 / 3.66 | FS, VS, VSE, VSS |
| C08 (108) | 21 x 54 7/16 | 21 1/2 x 54 15/16 | 19 1/2 x 52 15/16 | 24 in | 5.55 / 4.53 | FS, VS, VSE, VSS |
| C12 (112) | 21 x 70 1/4 | 21 1/2 x 70 3/4 | 19 1/2 x 68 3/4 | 24 in | 7.36 / not offered | FS only |
| D26 (150) | 22 1/2 x 22 15/16 | 23 1/4 x 23 7/16 | 21 1/4 x 21 7/16 | 24 in | 2.13 / not offered | FS only |
| D06 (156) | 22 1/2 x 45 3/4 | 23 1/4 x 46 1/4 | 21 1/4 x 44 1/4 | 24 in | 4.98 / not offered | FS only |
| M02 (302) | 30 1/16 x 30 | 30 9/16 x 30 1/2 | 28 9/16 x 28 1/2 | 16 in | 4.29 / 3.69 | FS, VS, VSS |
| M04 (304) | 30 1/16 x 37 7/8 | 30 9/16 x 38 3/8 | 28 9/16 x 36 3/8 | 16 in | 5.69 / 4.65 | FS, VS, VSE, VSS |
| M06 (306) | 30 1/16 x 45 3/4 | 30 9/16 x 46 1/4 | 28 9/16 x 44 1/4 | 16 in | 7.08 / 5.94 | FS, VS, VSE, VSS |
| M08 (308) | 30 1/16 x 54 7/16 | 30 9/16 x 54 15/16 | 28 9/16 x 52 15/16 | 16 in | 8.61 / 7.36 | FS, VS, VSE, VSS |
| S01 (601) | 44 1/4 x 26 7/8 | 44 3/4 x 27 3/8 | 42 3/4 x 25 3/8 | 16 or 24 in | 5.80 / 4.57 | FS, VS, VSE, VSS |
| S06 (606) | 44 1/4 x 45 3/4 | 44 3/4 x 46 1/4 | 42 3/4 x 44 1/4 | 16 or 24 in | 11.02 / 9.51 | FS, VS, VSE, VSS |
Source: VELUX America Skylight Measurement Guide (v-5859, March 2026) for rough opening, outside frame, finished drywall, framing fit, daylight area and legacy codes; model availability from the VELUX USA Skylight Size Guide. Deck-mounted units are rated for 14 to 85 degree roofs (3:12 to 137:12).
Daylight area is the glass you actually see, and VELUX lists a smaller figure for venting units largely because the operable sash adds frame inside the same opening. That is why a VS C06 delivers about 3.66 square feet of daylight against 4.56 for an FS C06 of the same rough opening.
VELUX curb-mounted skylight size chart
A VELUX curb-mounted code is the inside curb dimension in inches, and the skylight sits over a wood curb built on the roof. The three numbers that matter are the inside curb, the outside curb (measured wood to wood, without flashing) and the maximum skylight clearance, which is the largest curb the unit will cover. Curb-mounted units suit low-slope roofs because VELUX rates them from 0 to 60 degrees.
Venting curb-mounted sizes (VCS, VCE, VCM)
Solar-powered VCS units come in 10 sizes; electric VCE and manual VCM come in seven. The three sizes only available as VCS are 3737, 4622 and 4630.
| Size code | Inside curb W x H (in) | Outside curb W x H (in) | Max skylight clearance W x H (in) | Models offered |
|---|---|---|---|---|
| 2222 | 22 1/2 x 22 1/2 | 25 1/2 x 25 1/2 | 26 5/8 x 26 5/8 | VCS, VCE, VCM |
| 2234 | 22 1/2 x 34 1/2 | 25 1/2 x 37 1/2 | 26 5/8 x 38 5/8 | VCS, VCE, VCM |
| 2246 | 22 1/2 x 46 1/2 | 25 1/2 x 49 1/2 | 26 5/8 x 50 5/8 | VCS, VCE, VCM |
| 3030 | 30 1/2 x 30 1/2 | 33 1/2 x 33 1/2 | 34 5/8 x 34 5/8 | VCS, VCE, VCM |
| 3046 | 30 1/2 x 46 1/2 | 33 1/2 x 49 1/2 | 34 5/8 x 50 5/8 | VCS, VCE, VCM |
| 3434 | 34 1/2 x 34 1/2 | 37 1/2 x 37 1/2 | 38 5/8 x 38 5/8 | VCS, VCE, VCM |
| 3737 | 37 1/2 x 37 1/2 | 40 1/2 x 40 1/2 | 41 5/8 x 41 5/8 | VCS only |
| 4622 | 46 1/2 x 22 1/2 | 49 1/2 x 25 1/2 | 50 5/8 x 26 5/8 | VCS only |
| 4630 | 46 1/2 x 30 1/2 | 49 1/2 x 33 1/2 | 50 5/8 x 34 5/8 | VCS only |
| 4646 | 46 1/2 x 46 1/2 | 49 1/2 x 49 1/2 | 50 5/8 x 50 5/8 | VCS, VCE, VCM |
Source: VELUX USA Skylight Size Guide and VELUX Skylight Measurement Guide (2026).
Fixed curb-mounted sizes (FCM)
The fixed FCM has the widest curb range VELUX offers: 18 standard sizes, including long formats like 2270 and 4672 that no venting model matches. VELUX notes that flashing kits are not available for 1943, 2347 and 3171, so those three need site-built flashing.
| Size code | Inside curb W x H (in) | Outside curb W x H (in) | Max skylight clearance W x H (in) | Daylight area (sq ft) |
|---|---|---|---|---|
| 1943 | 19 1/2 x 43 1/2 | 22 1/2 x 46 1/2 | 23 5/8 x 47 5/8 | 3.88 |
| 2222 | 22 1/2 x 22 1/2 | 25 1/2 x 25 1/2 | 26 5/8 x 26 5/8 | 2.05 |
| 2230 | 22 1/2 x 30 1/2 | 25 1/2 x 33 1/2 | 26 5/8 x 34 5/8 | 3.05 |
| 2234 | 22 1/2 x 34 1/2 | 25 1/2 x 37 1/2 | 26 5/8 x 38 5/8 | 3.54 |
| 2246 | 22 1/2 x 46 1/2 | 25 1/2 x 49 1/2 | 26 5/8 x 50 5/8 | 5.03 |
| 2270 | 22 1/2 x 70 1/2 | 25 1/2 x 73 1/2 | 26 5/8 x 74 5/8 | 8.01 |
| 2347 | 23 1/2 x 47 1/2 | 26 1/2 x 50 1/2 | 27 5/8 x 51 5/8 | 5.44 |
| 3030 | 30 1/2 x 30 1/2 | 33 1/2 x 33 1/2 | 34 5/8 x 34 5/8 | 4.41 |
| 3046 | 30 1/2 x 46 1/2 | 33 1/2 x 49 1/2 | 34 5/8 x 50 5/8 | 7.28 |
| 3055 | 30 1/2 x 55 1/2 | 33 1/2 x 58 1/2 | 34 5/8 x 59 5/8 | 8.91 |
| 3171 | 32 x 72 | 35 x 75 | 36 1/8 x 76 1/8 | 12.55 |
| 3422 | 34 1/2 x 22 1/2 | 37 1/2 x 25 1/2 | 38 5/8 x 26 5/8 | 3.43 |
| 3434 | 34 1/2 x 34 1/2 | 37 1/2 x 37 1/2 | 38 5/8 x 38 5/8 | 5.92 |
| 3446 | 34 1/2 x 46 1/2 | 37 1/2 x 49 1/2 | 38 5/8 x 50 5/8 | 8.41 |
| 4622 | 46 1/2 x 22 1/2 | 49 1/2 x 25 1/2 | 50 5/8 x 26 5/8 | 4.81 |
| 4630 | 46 1/2 x 30 1/2 | 49 1/2 x 33 1/2 | 50 5/8 x 34 5/8 | 7.13 |
| 4646 | 46 1/2 x 46 1/2 | 49 1/2 x 49 1/2 | 50 5/8 x 50 5/8 | 11.79 |
| 4672 | 46 1/2 x 72 1/2 | 49 1/2 x 75 1/2 | 50 5/8 x 76 5/8 | 19.36 |
Source: VELUX USA Skylight Size Guide; daylight area and flashing-kit notes from the VELUX Skylight Measurement Guide (2026).
Undersized-curb and custom FCM sizes
For old curbs smaller than the standard grid, VELUX sells four undersized-curb FCM sizes (2020, 2044, 3232 and 4444). They ship with LowE3-366 laminated glass only, and VELUX does not offer flashing kits for them.
| Size code | Outside curb W x H (in) | Inside curb W x H (in) | Max skylight clearance W x H (in) | Source |
|---|---|---|---|---|
| 2020 | 24 x 24 | 21 x 21 | 25 1/8 x 25 1/8 | VELUX 2026 guide |
| 2044 | 24 x 48 | 21 x 45 | 25 1/8 x 49 1/8 | VELUX 2026 guide |
| 3232 | 36 x 36 | 33 x 33 | 37 1/8 x 37 1/8 | VELUX 2026 guide |
| 4444 | 48 x 48 | 45 x 45 | 49 1/8 x 49 1/8 | VELUX 2026 guide |
When no standard or undersized code fits, VELUX builds a custom FCM to the maximum skylight clearance, which it calculates by rounding the outside curb dimension up to the nearest 1/4 inch and adding 1 inch for roofing and flashing. Custom sizes carry their own lead times and no flashing kit; our guide to custom skylights and non-standard sizes covers when that route is worth it.
VELUX Sun Tunnel sizes
VELUX Sun Tunnel tubular skylights come in 10, 14 and 22 inch diameters, and each needs two openings: a roof deck cutout and a ceiling cutout. Rigid tunnels (TGR, TMR) carry light farther, up to 40 feet for the 22 inch TGR, while the flexible TGF is limited to 8 or 12 feet but bends around attic obstructions. All three models below are rated for 14 to 60 degree roofs.
| Model and diameter | Ceiling rough opening (in) | Roof deck rough opening W x H (in) | Tube in kit | Max recommended run | Source |
|---|---|---|---|---|---|
| TGR low-profile rigid, 10 in | 11 1/4 | 10 1/2 x 16 | 4 ft | 20 ft | VELUX TGR page |
| TGR low-profile rigid, 14 in | 15 1/4 | 14 1/2 x 18 | 4 ft | 30 ft | VELUX TGR page |
| TGR low-profile rigid, 22 in | 23 1/4 | 22 1/2 x 26 | 4 ft | 40 ft | VELUX TGR page |
| TMR pitched rigid, 10 in | 11 1/4 | 12 1/2 x 16 | 4 ft | 30 ft | VELUX TMR page |
| TMR pitched rigid, 14 in | 15 1/4 | 14 1/2 x 20 | 4 ft | 30 ft | VELUX TMR page |
| TGF low-profile flexible, 14 in | 14 3/4 | 14 1/2 x 18 | 8 ft | 8 ft | VELUX TGF page |
| TGF low-profile flexible, 22 in | 22 3/4 | 22 1/2 x 26 | 8 ft | 12 ft | VELUX TGF page |
The 14 inch size is the one with the most options: VELUX also makes the flat-glass TLR and the curb-mounted TCR in 14 inch rigid only. Check both cutouts against your framing. A 16 inch on-center bay is 14 1/2 inches clear, so the 14 inch roof deck cut fits it exactly, but the 14 inch ceiling cut (15 1/4 inches rigid, 14 3/4 flexible) is slightly wider than a 16 inch on-center joist bay and fits easily in a 24 inch truss bay. The 10 inch fits a 16 inch bay at both roof and ceiling.
Which VELUX skylight size fits between your rafters?
A VELUX skylight fits without cutting framing when its rough opening width is no wider than the clear space between rafters. With standard 1 1/2 inch thick lumber, rafters 24 inches on center leave a 22 1/2 inch bay and rafters 16 inches on center leave 14 1/2 inches. That is why the C and D widths suit 24 inch framing and the A width suits 16 inch framing.
The table below works through that arithmetic against VELUX’s published rough opening widths. The “fits on center” ratings are VELUX’s; the clear-bay math is The Roofing Brief’s, assuming nominal 2x rafters at exact spacing, so measure your actual bay before ordering.
| Rafter spacing | Clear bay (one bay) | Codes that fit one bay | Clear span if one rafter is headed off | Codes that fit after heading off | Source |
|---|---|---|---|---|---|
| 16 in on center | 14 1/2 in | A06 (14 1/2 in wide, exact fit); 10 in Sun Tunnel; 14 in Sun Tunnel roof cut | 30 1/2 in (two bays) | M02, M04, M06, M08 (30 1/16 in wide) | VELUX fit ratings; TRB bay math |
| 24 in on center | 22 1/2 in | C01 to C12 (21 in wide, fur out 3/4 in each side); D26, D06 (22 1/2 in, exact fit); 22 in Sun Tunnel roof cut | 46 1/2 in (two bays) | S01, S06 (44 1/4 in wide) | VELUX fit ratings; TRB bay math |
| 16 in on center, two rafters headed off | 14 1/2 in | Not applicable | 46 1/2 in (three bays) | S01, S06 | VELUX fit ratings; TRB bay math |
Cutting a rafter is a structural change. The International Residential Code (IRC Section R802.9) requires openings in roof framing to be framed with headers and trimmers, and requires doubled headers and trimmers once the header span passes 4 feet. Trussed roofs are stricter: IRC R802.10.4 says truss members shall not be cut or altered without approval from a registered design professional. That is one practical reason VELUX describes the D26 and D06 as fitting “perfectly between roof trusses”: they need no cut at all on 24 inch truss spacing. Local codes and permit requirements vary, so confirm with your building department.
How to measure an existing VELUX skylight for replacement
The fastest way to size a replacement VELUX skylight is to read the product tag, not a tape measure. VELUX skylights carry an ID tag, and the glass spacer bar between the panes carries a Velterm number that VELUX can trace back to the unit. Measure only when the tag is missing, and then measure the finished drywall opening for deck-mounted units or the outside curb for curb-mounted units.
- Find the tag. On fixed and venting deck-mounted skylights (FS, VS, VSE, VSS), VELUX places the tag at the interior bottom left of the frame; on venting models you may need to open the sash to see it. Curb-mounted units (FCM, VCM, VCS, VCE) carry the tag on the exterior, on one of the four sides.
- Read the size from the tag. Current tags list the unit type, unit size and a variant code, such as FS C06. If the tag shows a three-digit size, convert it with the crosswalk in the deck chart above (for example 104 = C04, 308 = M08).
- Check the glass spacer bar if the tag is gone. The Velterm number sits in the top right corner of the spacer bar between the panes. VELUX’s guide shows that current Velterm codes include the pane size and manufacture year, and VELUX customer service can use it to identify the unit.
- Deck-mounted with no tag: measure the finished drywall opening. Measure the light shaft width and height at the ceiling of the skylight frame, finished surface to finished surface, then match both numbers to the ranges in the table below.
- Curb-mounted with no tag: measure the outside curb. VELUX’s rule is wood to wood, excluding flashing and roofing. Match that outside curb dimension to the curb charts above, or use it to order a custom FCM.
- Record roof pitch and roofing type. Deck-mounted VELUX units need at least 14 degrees (3:12); below that, a curb-mounted unit is the usual answer. Our roof pitch chart converts degrees to rise-over-run.
VELUX publishes finished-opening ranges for replacement work, because drywall returns vary by a fraction of an inch from house to house. Match the width to a letter and the height to a number.
| If your finished opening measures | It points to | Source |
|---|---|---|
| Width 13 1/4 to 15 1/4 in | A (A06) | VELUX 2026 guide |
| Width 19 1/2 to 21 1/2 in | C (C01, C04, C06, C08, C12) | VELUX 2026 guide |
| Width 21 1/4 to 23 1/4 in | D (D26, D06) | VELUX 2026 guide |
| Width 28 1/2 to 30 1/2 in | M (M02, M04, M06, M08) | VELUX 2026 guide |
| Width 42 3/4 to 44 3/4 in | S (S01, S06) | VELUX 2026 guide |
| Height 21 7/16 to 23 7/16 in | 26 (D26) | VELUX 2026 guide |
| Height 25 3/8 to 27 3/8 in | 01 (C01, S01) | VELUX 2026 guide |
| Height 28 1/2 to 30 1/2 in | 02 (M02) | VELUX 2026 guide |
| Height 36 3/8 to 38 3/8 in | 04 (C04, M04) | VELUX 2026 guide |
| Height 44 1/4 to 46 1/4 in | 06 (A06, C06, D06, M06, S06) | VELUX 2026 guide |
| Height 53 to 55 in | 08 (C08, M08) | VELUX 2026 guide |
| Height 68 3/4 to 70 3/4 in | 12 (C12) | VELUX 2026 guide |
The C and D width ranges overlap between 21 1/4 and 21 1/2 inches. A finished width in that band could be either, so confirm with the tag, the Velterm number or VELUX customer service before ordering, since the flashing kit is cut to the exact size code. If the old unit is being replaced during a reroof, our skylight installation cost guide shows how size and type move the installed price.
VELUX roof window sizes are a separate chart
VELUX roof windows use two-letter, two-digit codes such as CK04 or MK08, and they are not the same sizes as the skylight codes C04 or M08. A top-hinged GPU MK08 needs a 31 1/4 x 55 1/2 inch rough opening, while an M08 skylight needs 30 1/16 x 54 7/16 inches. Mixing them up is an easy ordering mistake, because a search for “MK08” often lands on a skylight chart.
| GPU size code | Rough opening W x H (in) | Outside frame W x H (in) | VELUX egress net clear opening (sq ft) |
|---|---|---|---|
| CK04 | 22 1/8 x 39 | 21 5/8 x 38 1/2 | Not listed |
| CK06 | 22 1/8 x 46 7/8 | 21 5/8 x 46 3/8 | Not listed |
| MK04 | 31 1/4 x 39 | 30 3/4 x 38 1/2 | Not listed |
| MK06 | 31 1/4 x 46 7/8 | 30 3/4 x 46 3/8 | 5.78 |
| MK08 | 31 1/4 x 55 1/2 | 30 3/4 x 55 | 6.92 |
| PK10 | 37 5/8 x 63 1/2 | 37 1/8 x 63 | 9.83 |
| SK06 | 45 3/8 x 46 7/8 | 44 7/8 x 46 3/8 | 8.76 |
| UK08 | 53 1/4 x 55 1/2 | 52 3/4 x 55 1/16 | 12.49 |
Source: VELUX Skylight Measurement Guide (2026). GPU roof windows are rated for 15 to 55 degree roofs. VELUX lists the five sizes with a net clear figure as emergency escape and rescue openings, and notes that code also limits the finished sill to 44 inches above the floor; the IRC egress minimum is generally 5.7 square feet of net clear opening, so check your local code. For the difference between the two product types, see our skylight vs roof window guide.
Which VELUX skylight size should you pick?
Pick the VELUX size by framing first, roof pitch second and daylight third. On a new opening, the cheapest and fastest install is usually the size that drops between existing rafters with no header. On a replacement, the right size is almost always the code on the old tag, because changing size means reframing and new drywall. These skylight options map common situations to a starting code.
| Your situation | Start with | Why |
|---|---|---|
| Replacing an existing VELUX | The code on the tag (or its modern equivalent of a three-digit code) | Same rough opening, same flashing kit size, no reframing |
| New opening, 24 in rafters or trusses, no cutting | C04, C06 or C08 (venting available); D06 if fixed is fine | Fits one 22 1/2 in bay; D sizes need no shimming |
| New opening, 16 in rafters, small room or hall | A06 fixed, or a 10 in Sun Tunnel | Both fit one 14 1/2 in bay with no header |
| Kitchen or living room, more light wanted | M06 or M08 (16 in framing), S06 for the most glass | 7.08 to 11.02 sq ft of daylight (fixed) per VELUX |
| Low-slope roof under 3:12 | A curb-mounted VCS, VCM or FCM size | Deck-mounted units need 14 degrees minimum; curb units go to 0 degrees |
| Closet, hallway or bathroom under an attic | 14 in Sun Tunnel (TGR rigid if the run is straight) | No drywall light shaft to build; roof cut fits a 16 in rafter bay |
| Old curb that matches no standard code | Undersized FCM (2020, 2044, 3232, 4444) or custom FCM | Built to the existing outside curb; flashing is site-built |
For pricing by model and how VELUX compares with Fakro and Sun-Tek, see our VELUX skylights review with 2026 costs. This page stays the dimensional reference.
Frequently asked questions
What does C06 mean on a VELUX skylight?
C06 is a VELUX deck-mounted size code. The C sets a 21 inch rough opening width and the 06 sets a 45 3/4 inch rough opening height, with an outside frame of 21 1/2 x 46 1/4 inches. The C06 is offered as a fixed FS and as all three venting models (VS, VSE, VSS), and it fits rafters 24 inches on center. Older VELUX units label the same size 106.
What is the rough opening for a VELUX M06?
A VELUX M06 needs a rough opening of 30 1/16 x 45 3/4 inches, and its outside frame measures 30 9/16 x 46 1/4 inches, per VELUX’s 2026 Skylight Measurement Guide. VELUX rates the M width for 16 inch on-center framing, which in practice means heading off one rafter to open two 14 1/2 inch bays into a 30 1/2 inch space. The M06 delivers about 7.08 square feet of daylight as a fixed unit.
What size VELUX skylight fits between rafters 24 inches on center?
Rafters 24 inches on center leave a 22 1/2 inch clear bay with standard 1 1/2 inch lumber. VELUX’s C sizes (21 inch rough opening width) fit that bay with a little shimming, and the D26 and D06 (22 1/2 inch width) fit it exactly, which VELUX describes as fitting perfectly between roof trusses. The C sizes come in venting models; the D sizes are fixed only.
Is a VELUX 2246 the same size as a C06?
No. A 2246 is a curb-mounted code meaning a 22 1/2 x 46 1/2 inch inside curb (25 1/2 x 49 1/2 inch outside curb), used by the VCS, VCE, VCM and FCM models. A C06 is a deck-mounted code with a 21 x 45 3/4 inch rough opening, used by the FS, VS, VSE and VSS. They suit similar rafter bays but use different mounting, flashing and framing details.
How do I find the size of my existing VELUX skylight?
Read the VELUX ID tag first. Deck-mounted units carry it at the interior bottom left of the frame; curb-mounted units carry it on the exterior. If the tag is missing, the Velterm number in the top right corner of the glass spacer bar identifies the unit. As a last resort, measure the finished drywall opening (deck-mounted) or the outside curb wood to wood (curb-mounted) and match it to VELUX’s size ranges.
What sizes do VELUX Sun Tunnels come in?
VELUX Sun Tunnel skylights come in 10, 14 and 22 inch diameters. The 14 inch TGR rigid model needs a 15 1/4 inch ceiling opening and a 14 1/2 x 18 inch roof deck opening, ships with 4 feet of tube, and VELUX recommends runs up to 30 feet. The flexible TGF comes in 14 and 22 inch only, with 8 feet of tube and a shorter maximum run of 8 to 12 feet.