Shiplap Calculator
Row count, starting row height, and the exact rip width of your last board — drawn on the wall.
Your estimate
You'll need 19 rows and 32 boards — about $384.
Last row rips to 3 3/4" · 228 linear feet of shiplap · 96 sq ft covered
Measurements
Row layout
1x6 shiplap ≈ 5.125 in
Shift this to move the top rip
Subtract doors and windows
No openings yet. Add each door or window and its area comes out of the total.
Waste & cost
10% is standard
Every row drawn to scale. The top band shows the rip width of your final board — adjust the starting row height to move it.
The breakdown
- Total rows
- 19
- Full-exposure rows
- 18
- Last row rip width
- 3 3/4"
- Board exposure
- 5 1/8"
- Wall area
- 96 sq ft
- Openings subtracted
- −0 sq ft
- Net coverage area
- 96 sq ft
- Linear feet of board
- 228 lf
- Waste overage (10%)
- 22.8 lf
- Boards to buy (8 ft)
- 32
- Estimated cost
- $384
Row plan
| Part | Cut length | Qty |
|---|---|---|
| Bottom starting row2 board(s) per row across 12' 0" | 5 1/8" | 2 |
| Full rows | 5 1/8" | 34 |
| Top row (rip to width) | 3 3/4" | 2 |
| Stock boards to buyIncludes waste overage | 8 ft | 32 |
Where to buy
Hand-picked search links for the materials on your list. As an Amazon Associate, ProjectMath earns from qualifying purchases.
Prices and availability are set by the retailer and change often. Always confirm the exact product size matches what this calculator assumed.
How this is calculated
Shiplap stacks by exposure, not by nominal board width. The bottom row height decides where every seam above it lands, which is why changing it by an inch can rescue an ugly rip at the ceiling.
- remaining height = wall height − bottom row height
- full rows = floor(remaining height ÷ exposure)
- last row rip = remaining height − full rows × exposure
- linear feet = total rows × wall width
- boards to buy = ceil(linear feet × (1 + waste) ÷ board length)
Exposure is the visible face after the lap closes — usually about 5 1/8 in for nominal 1x6 shiplap.
- 1Measure the surfaceMeasure the width and height (or length) of the area in feet, inches, or meters and enter them in the calculator.
- 2Enter board exposureUse the exposed face height of the board, not the nominal size — a 1x6 shiplap typically exposes about 5.125 inches once the rabbet is lapped.
- 3Tune the starting rowAdjust the first row height to move where the last rip lands, so you avoid a sliver at the ceiling.
- 4Add a waste overageKeep the default 10% waste allowance for cuts and mistakes, or adjust it for complex layouts and diagonal patterns.
- 5Read the shopping listThe calculator rounds up to whole units to buy and multiplies by your price per unit for an estimated total. Copy or print the plan and take it to the store.
Common questions
How do I calculate how much shiplap I need?
Divide your wall height by the board's exposure — the visible face after the lap, about 5.125 inches for 1x6 shiplap — to get the row count. Multiply rows by wall width for linear feet, add 10% waste, and divide by the board length. The calculator above does all of it and shows the exact last-row rip.
How many shiplap boards do I need for a 12 foot wall?
An 8 foot tall, 12 foot wide wall at 5.125 inch exposure takes about 19 rows — roughly 228 linear feet, or 31 eight-foot boards with 10% waste. Enter your own wall size above for the exact count.
How do I avoid a thin sliver board at the ceiling?
Change the height of the bottom starting row. Shifting it by an inch or two redistributes the whole wall and can turn a half-inch sliver into a comfortable three-inch top row.
Should shiplap start at the floor or the ceiling?
Start at the bottom and work up so gravity holds each board on the one below. Plan the layout first so the awkward rip lands at the floor behind trim, or at the ceiling behind crown.
What is board exposure?
Exposure is the visible height of each board after the lap overlaps the one below. Nominal 1x6 shiplap is 5.5 inches wide and usually exposes about 5.125 inches.
How much waste should I add for shiplap?
10% is standard for a plain rectangular wall. Go to 15% when the wall has several openings or you are running boards on a diagonal.
A worked example: an 8 × 12 ft wall
Say your wall is 8 ft (96 in) tall and 12 ft wide, with 1x6 shiplap exposing 5.125 in per row. Here is the math the calculator runs:
- 1. Count the rows. 96 ÷ 5.125 = 18.7 rows — 18 full rows plus a top row ripped to 3.6 in.
- 2. Check the top rip. 3.6 in at the ceiling is comfortable. If it were a half-inch sliver, you'd shift the starting row height until the top row landed above 3 in.
- 3. Total the boards. 19 rows × 12 ft = 228 linear feet. Add 10% waste (251 lf) and divide by 8 ft boards: 32 boards to buy.
- 4. Price it out. At $12 per board, the wall lands around $384 before trim — enter your local price above for your number.
Mistakes that waste boards
- Counting by nominal width. A 1x6 board only shows about 5 1/8 in once the lap closes. Plan with 6 in rows and you'll come up nearly two boards short on an 8 ft wall.
- Ignoring the last row. Walls almost never divide evenly. Find out before you start whether the ceiling row is a full board or a sliver — moving the starting row an inch can fix it for free.
- Starting at the ceiling. Work from the floor up so each board rests on the one below while you nail. Gravity is your extra set of hands.
- Buying exact linear feet. Knot holes, bad tongues, and off-square corners eat boards. The 10% overage is cheaper than a second trip to the yard.