Interior Shiplap Calculator
How much shiplap do you actually need? A "1×6" shiplap board never covers 6 inches of wall — the rabbet or tongue and the nickel-gap reveal eat into the exposed face, so a UFP-Edge Timeless 1×6 really covers just 4-5/8". This free shiplap calculator solves every row or run from that real coverage width, using a verified profile catalog with manufacturer-sourced numbers instead of guessing.
Pick from traditional rabbeted pine, UFP-Edge Timeless nickel-gap, Woodtone penny-gap, T&G pattern pine, or your own faux-ripped plywood strips. Add every wall (with doors and large windows deducted, small openings left alone on purpose), choose horizontal or vertical orientation, flag a ceiling run, and get a full bill of materials: boards or packs (nickel-gap lines are sold by the published-coverage multi-pack, not the piece), fasteners, construction adhesive, and caulk.
Interior only, quantities only — no pricing, no signup. Waste factors step up automatically for staggered butt joints, openings-heavy walls, ceilings, and vertical runs. It hands baseboard and casing transitions to the Trim Calculator, paintable area to the Interior Paint Calculator, and exterior lap siding to the Lap Siding and HardiePlank calculators.
This tool covers interior shiplap only — boards, packs, fasteners, adhesive, and caulk. For baseboard, casing, and running-trim linear feet, use the Trim & Baseboards Calculator. For exterior lap siding, see the Lap Siding or HardiePlank Calculator.
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Interior Shiplap Calculator
Get an exact board or pack count from the real EXPOSED coverage width — not the nominal or actual board width — across a verified profile catalog (traditional rabbeted pine, UFP-Edge Timeless nickel-gap, Woodtone, T&G pattern pine, or your own faux-ripped strips). Handles horizontal or vertical runs, ceilings, butt-joint staggering, and a full bill of materials: boards or packs, fasteners, caulk, and adhesive. Free, no signup, quantities only.
Profile & coverage width
Source: Wayfair/Lowe's listing: "4-5/8-inch exposed face width"; 18.48 sq ft per 6-pack at 8'
Walls
No openings entered. Small openings (outlets, single small windows) are never deducted — only large ones (doors, windows ≥15 sq ft).
Orientation, ceiling & waste
Corners & termination
Three things that decide a shiplap take-off
Shiplap math lives and dies on one number — the net coverage width — and on two layout decisions the store never mentions: what the last row rips to, and where the butt joints land when a wall outruns the boards. These engineering-style diagrams cover each one.
The first diagram is why a “1×6” never covers 6 inches. A rabbeted board laps its neighbor by ½″, and a tongue-and-groove board loses its tongue plus the nickel-gap reveal — so the same nominal size covers 5″, 4⅝″, or 5⅛″ depending on the profile. The calculator’s profile catalog stores the verified coverage per SKU, and every count is solved from it.
The second diagram is the row math itself: wall height divided by coverage, rounded up. An 8-ft wall in nickel-gap 1×6 works out to 21 rows — 252 lineal feet on a 12-ft wall before waste — with a 3½″ rip at the top. The pro move is to split that difference between the first and last rows so neither is a sliver.
The third diagram is joint placement on walls longer than the stock. Every butt joint must land on a stud, and the seams should stagger so no joint repeats within about three rows — stacked joints read as one vertical seam and open up as the boards move. This is also why the calculator holds waste at a 12% minimum whenever staggering is needed.
Calculation Formulas
The single biggest source of error: a "1×6" is never 6 inches of wall. Coverage is what actually shows after the next board laps or tongues over it and the reveal gap is subtracted. Every row/run count below uses this number, never the nominal or actual milled width.
Example:
UFP-Edge Timeless 1×6 is milled to 5-5/16" wide with a T&G nickel-gap joint, but the published EXPOSED FACE is 4-5/8" — that 4-5/8" is what the solver uses.
Horizontal shiplap climbs the wall in rows. The last row almost never lands exactly on the ceiling line, so the trade convention is to rip the FIRST and LAST rows to equal widths ("split the difference") rather than leaving a full first row and a sliver last row.
Example:
An 8-ft wall (96") with 4-5/8" coverage: 96 ÷ 4.625 = 20.75 → 21 rows, with the first and last ripped to ~4.5" each.
Vertical shiplap rotates the same solver 90° — runs replace rows, and each run spans the full wall height. Vertical runs require horizontal furring strips (or a plywood substrate) every 16"–24" because studs run the wrong direction to nail into across the board length.
Example:
A 12-ft wall (144") with 5" coverage (traditional pine 1×6): 144 ÷ 5 = 28.8 → 29 runs.
Any row or run longer than the stock length needs a butt joint. The trade rule is to land every joint on a stud and stagger the seam pattern across rows so joints don't stack within about 3 rows (avoid an "H" pattern) — which is exactly why the waste band steps up to 12–15% once a wall exceeds stock length.
Example:
A 20-ft wall run with 12-ft stock: ceil(20 ÷ 12) = 2 pieces per row, with one staggered seam per row.
A quantities calculator that deducts every outlet or small window under-orders, because the off-cuts around small openings are usually too short to reuse. The waste factor is what absorbs that loss — deducting small openings AND applying full waste double-counts the savings.
Example:
A wall with one 32"×80" door (17.8 sq ft) and one 24"×18" outlet-height window (3 sq ft): only the door is deducted; the window stays in the gross area.
Waste is not one flat number — it steps up with the scenario. A simple wall defaults to 10%; a ceiling, a staggered-joint wall, or an openings-heavy wall bumps the floor to 15% (12% for stagger alone); vertical orientation adds another 5% on top for the furring-strip layer.
Example:
A ceiling installation with staggered joints: max(10, 15, 12) = 15%, unchanged by vertical since it's horizontal-on-a-ceiling.
Nickel-gap product lines are sold by the multi-pack with a published square-foot coverage, not by the individual board — a UFP-Edge 1×6×8' 6-pack covers 18.48 sq ft. Converting board count to packs (not the reverse) is why calculators that only do area ÷ nominal width leave buyers short.
Example:
A 105 sq ft coverage need in UFP-Edge Timeless 1×6×8' (18.48 sq ft/6-pack): ceil(105 ÷ 18.48) = 6 packs = 36 boards.
Perimeter seams and inside corners get caulked before priming, same design value as the shipped Board & Batten calculator: ~50 LF per 10-oz tube at a fine 1/8"–1/4" trim bead, plus 10% waste.
Example:
A 12×20-ft room (64 LF perimeter) with 4 corners at 8 ft: (128 + 32) × 1.10 ÷ 50 ≈ 4 tubes.
One bead runs down the back of each board when installing over drywall — PPG Liquid Nails LN-903 Heavy Duty coverage, ~30 LF per 10-oz tube at a 1/4" bead. Real wood over open studs with a strong mechanical fastening schedule can skip adhesive.
Example:
252 LF of boards over drywall: ⌈252 ÷ 30⌉ = 9 tubes.
Real wood is blind-nailed through the rabbet lip or T&G tongue plus face-nailed top and bottom into studs at 16" o.c., 1-1/4"–1-1/2" of penetration into solid wood. MDF has no structural rabbet strength, so it is face-nailed only, at roughly one fastener per linear foot, with ends pre-drilled to avoid blowout.
Example:
252 LF of real-wood shiplap: ⌈252 × 1.5⌉ = 378 finish nails; the same run in MDF: ⌈252 × 1.0⌉ = 252 brads.
Standard Constants
| Constant | Value | Description |
|---|---|---|
| Traditional Rabbeted Pine | 1×6 ≈ 5.0" · 1×8 ≈ 6.5" coverage | Lumber & Supply Co. and mill catalogs list traditional rabbeted-shiplap coverage at roughly 5" for a 1×6 and 6.5" for a 1×8 — varies mill to mill by lap depth, PS 20 fixes only the lap width (3/8"–1/2"), not the exact exposed face. |
| UFP-Edge Timeless Nickel-Gap | 1×6 = 4-5/8" · 1×8 = 6-5/16" coverage | Manufacturer-published exposed face widths (Wayfair/Lowe's/Home Depot listings). The 1×8 figure on ufpedge.com itself duplicates the 1×6 value (4.625") — a documented copy-paste error; use the Home Depot 6-5/16" figure and verify per-SKU. |
| UFP-Edge Pack Coverage | 1×6×8' = 6-pack / 18.48 sq ft | Nickel-gap MDF/pine is sold by the published-coverage multi-pack at home centers, not the individual board — the reason a UFP-Edge reviewer reported being short on an 11×14 kitchen "by 9 boxes" when estimating from raw square footage alone. |
| Woodtone Shiplap | 1×6 = 4-3/4" · 1×8 = 6-1/2" coverage, 12-ft only | Woodtone markets a "penny gap" (not "nickel gap") T&G profile, sold only in 12-ft lengths — its own product page resolved an internal length inconsistency in favor of 12' only. |
| Nickel Gap | ~1/8" reveal | The thickness of a US nickel. It is a LOOK, not strictly a joint type — modern "nickel gap" products achieve it with an interlocking T&G profile with a built-in spacer, producing a shiplap-style shadow line without a true rabbet. |
| Waste Factor Bands | 10% simple · 12–15% stagger/openings/ceiling · +5% vertical | Retailer and contractor estimating-guide consensus. Diagonal/herringbone (~15%) is a footnote only — not a v1 layout mode on this calculator. |
| Last-Row/Run Minimum | 2" minimum rip | Below a 2" sliver, re-plan the starting line and split the first/last row or run evenly instead — the finish-carpentry "split the difference" convention. |
| Fastener Penetration | 1-1/4"–1-1/2" into solid wood | UFP-Edge FAQ: fasten with 15- or 16-gauge trim nails long enough to reach 1-1/4"–1-1/2" of penetration into solid wood framing. |
| Acclimation & Expansion | 48–72 hr · 1/16"–1/32" board-end gap | Boards acclimate in the install room for 48–72 hours, stacked off the floor with air circulating (Metrie: minimum 48 hr; Menards: at least 72 hr). Leave a small gap at board ends for wood movement; the nickel/penny reveal covers the field gap. |
Note: All calculations include appropriate waste factors based on project complexity and material type. Results are estimates and should be verified by professionals before purchasing materials.
PS 20-20 American Softwood Lumber Standard(PS 20)
View StandardThe ALSC voluntary product standard defining lap and tongue widths for worked lumber: "the tongue shall be 6 mm (1/4 inch) wide in tongued and grooved lumber and the lap shall be 10 mm (3/8 inch) or 13 mm (1/2 inch) wide in shiplapped lumber," plus S4S nominal-to-actual dimensions.
Key Requirements:
- •Shiplap lap width: 3/8" or 1/2" (worked lumber under nominal 2" thick)
- •T&G tongue width: 1/4"
- •1× boards finish to 3/4" thick (S4S)
- •Always compute row/run counts from the net EXPOSED coverage width, never nominal or actual width
- •Confirm the milled profile of your specific stock — mills vary the lap depth within the PS 20 range
ANSI A208.2 (MDF)(ANSI A208.2)
View StandardThe American National Standard for medium density fiberboard, governing density, bond strength, and formaldehyde emission classes for MDF trim and panel products used in nickel-gap and faux-shiplap builds.
Key Requirements:
- •MDF has no structural rabbet/tongue strength — face-nail only
- •Pre-drill near board ends to prevent splitting
- •Not rated for wet areas — swells with moisture
- •Seal cut edges when priming for moisture resistance in borderline rooms
EPA TSCA Title VI / CARB Phase 2(TSCA VI / CARB 2)
View StandardFederal and California formaldehyde-emission limits for composite wood products, including MDF shiplap and nickel-gap panel stock.
Key Requirements:
- •Composite wood products sold in the US must carry TSCA Title VI compliance labeling
- •CARB Phase 2 sets the stricter of the two limits for products sold into California
- •Check the compliance label before selecting a nickel-gap MDF product for an occupied space
WMMPA / MMPA "WM" Moulding Profile Catalog(WM series)
View StandardThe Moulding & Millwork Producers Association standardized "WM" profile framework — the same catalog referenced by the Board & Batten calculator — covers cap-rail and termination trim used with partial-height shiplap runs.
Key Requirements:
- •Cap-rail / panel-mould family WM166, WM163 fit a partial-height shiplap cap
- •Rabbeted wainscot cap WM294 (1-1/8" × 11/16") is a common shiplap top termination
- •Profile numbers are consistent across manufacturers, unlike proprietary names
Manufacturer Install & Fastening Guides (UFP-Edge / WindsorONE / Metrie)(Mfr. guides)
View StandardFastening, acclimation, and moisture guidance the calculator reflects: blind-nail through the lip/tongue plus face-nail top and bottom into studs for real wood; face-nail only for MDF; 48–72 hr acclimation; low-moisture rooms only.
Key Requirements:
- •Real wood: 15/16-ga finish nails, blind through the lip + face into studs at 16" o.c.
- •MDF: 15–18-ga brad/pin nails, face-nail only, pre-drill near ends
- •Do not create an "H" seam pattern on runs longer than 16 ft
- •Real wood, MDF, and primed pine are low-moisture interior products only — not for showers or standing water
Standards Disclaimer: Standards and codes are subject to periodic updates. Always verify current requirements with local building authorities and professional engineers before beginning construction. Links provided are for reference only.
Terminology: Shiplap vs. Nickel Gap vs. T&G vs. Faux
Four different joints, one visual family
True (rabbeted) shiplap has an L-shaped rabbet milled into opposite faces so boards overlap and lie flat, with the gap set by the installer. "Nickel gap" is a look, not strictly a joint — modern products achieve the ~1/8" reveal with an interlocking T&G profile and a built-in spacer. Plain T&G can install tight (no gap) or with a reveal. "Faux shiplap" is square-edged strips relying entirely on a spacer and face-nails/adhesive for the look.
Regional Examples:
Material by Room (moisture)
Real wood and MDF are low-moisture only
Primed pine, poplar, and MDF shiplap are all for dry interiors. None of them are rated for a shower or standing-water area — that is a PVC/AZEK job, which is outside this interior calculator's core scope but worth flagging before a bathroom accent wall goes in.
Regional Examples:
Horizontal vs. Vertical Orientation
Vertical needs a furring layer studs don't provide
Horizontal shiplap nails straight into vertical studs. Vertical shiplap runs the wrong direction relative to framing, so it needs horizontal furring strips (or a plywood substrate) every 16"–24" to give every board something to nail into across its length.
Regional Examples:
Long Walls: Butt Joints & Staggering
Walls longer than stock length need a plan
Any wall (or wall height, for vertical runs) longer than the stock length you're buying needs a butt joint. The trade convention is to land every joint on a stud and stagger the seam pattern row to row so no "H" pattern forms — which consumes more off-cuts and is why the waste band steps up to 12–15% once this triggers.
Regional Examples:
Openings: What to Deduct
Small openings stay in; large ones come out
The trade convention for a quantities calculator is to deduct only openings large enough that the off-cuts around them are still reusable — doors, and windows at or above about 15 sq ft. Smaller openings (outlets, single small windows) are left in the gross area because the waste factor already accounts for the extra cutting.
Regional Examples:
Before You Build
- •Contact your local building department for specific requirements
- •Verify frost line depths, wind zones, and seismic requirements for your area
- •Check if permits are required and schedule required inspections
- •Consult with a local contractor familiar with local codes
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How to Use This Calculator
- Pick a shiplap profile from the verified catalog (or enter a custom coverage width for faux-ripped plywood) and confirm the stock length.
- Add every wall with its length and height. Add any doors or large windows (≥15 sq ft) as openings — small openings are intentionally not deducted.
- Choose horizontal or vertical orientation, and flag it as a ceiling if the boards will run perpendicular to the joists.
- Set corner treatment and, for a partial-height run, a cap rail or ledge.
- Calculate: read the row or run count per wall, the boards or packs to buy, and a full bill of materials with fasteners, adhesive, and caulk. Copy or print it.
Why Coverage Width Beats Board Width
Every published nominal or actual board width overstates how much wall a shiplap board actually covers, because the rabbet, tongue, or reveal is designed to disappear under the next board. Manufacturer listings publish the real EXPOSED FACE width for exactly this reason — UFP-Edge Timeless 1×6 is milled to 5-5/16" but exposes only 4-5/8"; Woodtone's 1×6 exposes 4-3/4"; traditional rabbeted pine 1×6 exposes about 5". Using the wrong number is the single most common reason DIYers come up boards short mid-installation.
Frequently Asked Questions
Why does a 1×6 shiplap board only cover about 4.6–5 inches?
Because the rabbet lap or T&G tongue that joins each board to the next disappears under the following board, and a nickel-gap reveal (about 1/8") is subtracted too — so the EXPOSED coverage width is always less than the actual milled width. PS 20-20 (ALSC) fixes the lap at 3/8"–1/2" and the T&G tongue at 1/4", but the exact exposed face varies by manufacturer: UFP-Edge Timeless 1×6 exposes 4-5/8" (per its own listing: "4-5/8-inch exposed face width"), Woodtone's 1×6 exposes 4-3/4", and traditional rabbeted pine 1×6 exposes about 5". Always use the published EXPOSED FACE number, never the nominal or actual board width, or you'll come up short.
What's the difference between shiplap, nickel gap, and tongue-and-groove?
True (rabbeted) shiplap has an L-shaped rabbet milled into opposite faces of each edge so boards overlap and lie flat, with the installer setting the gap. "Nickel gap" is a LOOK, not strictly a joint type — modern nickel-gap products (UFP-Edge, Woodtone, Metrie) achieve the ~1/8" reveal with an interlocking tongue-and-groove profile that has a built-in spacer, so it's technically T&G producing a shiplap-style shadow line (Stikwood: "Nickel gap IS a type of tongue-and-groove paneling"). Plain tongue-and-groove can install tight with no gap at all (like beadboard) or with a reveal. "Faux shiplap" is square-edged strips (often ripped plywood) relying entirely on a spacer and face-nails/adhesive, with no rabbet or tongue at all.
How much waste should I add for a shiplap wall?
10% is the baseline for a simple wall with no butt joints. That climbs to 12–15% once a wall is longer than your stock length and needs staggered butt joints, and to 15% for openings-heavy walls or ceilings (more drops and breakage working overhead). Vertical orientation adds another 5% on top of whatever horizontal band applies, because of the furring-strip layer. This calculator auto-detects staggering, ceilings, and vertical runs and bumps the waste floor accordingly — you only need to raise it manually for something unusual.
Do I need to deduct doors and windows from my shiplap wall?
Deduct doors and large windows (roughly 15 sq ft or more) — treat them like a door-sized hole. Do NOT deduct small openings like outlets or a single small window: the off-cuts around them are usually too short to reuse, so deducting them and then applying the waste factor on top would double-count the savings and leave you short. This calculator follows that convention automatically based on opening size and type.
Can I install shiplap on a ceiling, and does it need different framing?
Yes — run the boards perpendicular to the ceiling joists so every board crosses a nailer, the same as horizontal shiplap crossing wall studs. If you want to run boards parallel to the joists instead, add blocking between the joists first so you have something to nail into. Ceilings also get bumped to the 12–15% waste band because overhead work generates more drops and breakage than a wall.
What's different about installing shiplap vertically?
Vertical shiplap runs perpendicular to your wall studs, so it needs horizontal furring strips (or a plywood substrate) installed roughly every 16"–24" first — otherwise there's nothing to nail into across the board's length (Metrie: "install strapping perpendicular to the studs roughly every 16 inches"). Toggle vertical orientation on this calculator and it adds a 5% waste bump for that extra furring layer and flags the framing note.
Do I blind-nail or face-nail shiplap, and is MDF different from real wood?
Real wood is blind-nailed through the rabbet lip or T&G tongue (hiding the fastener), plus face-nailed top and bottom into studs at 16" o.c. — UFP-Edge's FAQ specifies 15- or 16-gauge trim nails long enough for 1-1/4"–1-1/2" of penetration into solid wood. MDF has no structural rabbet strength, so it's face-nailed only with 15–18-gauge brads, with ends pre-drilled to prevent blowout. Adhesive-assisted installation over drywall is common for both, but mechanical fasteners into framing or furring strips are still required.
How is nickel-gap shiplap sold, and does this calculator include prices?
Nickel-gap MDF and pine lines are typically sold by the multi-pack with a published square-foot coverage at home centers, not by the individual board — for example, a UFP-Edge Timeless 1×6×8' 6-pack covers 18.48 sq ft. This calculator converts your board count into packs using that published coverage so you don't under-order (a real UFP-Edge reviewer reported coming up "short... by 9 boxes" estimating from raw square footage alone). On price: no — like every calculator on this site, it's quantities-only, giving you board or pack counts, lineal feet, fasteners, adhesive, and caulk, not dollar figures.