Calculator · Interiors & furniture
Board and Batten, Wainscoting and Shiplap Layout Calculator
Lay out board and batten or wainscoting with equal bays and no skinny end panel, plus shiplap courses, rip widths, linear length and stock lengths to buy.
Wall panel layout calculator
Board and batten and wainscoting mode solves for equal bays so there is no narrow leftover panel at one end. Shiplap mode counts horizontal courses and the rip width of the last one.
Result
Enter the wall and board sizes, then calculate an equal-bay layout or a shiplap course plan.
How it works
Board and batten and most wainscoting styles look right only when every bay is the same width. Picking a spacing such as 400 mm or 16 in and marking it from one end almost always leaves a narrow sliver of panel at the other end. This calculator works the other way round: it fixes the wall width and batten width, then finds the whole number of equal bays whose gap is closest to the spacing you want.
You can also enter an exact number of bays, choose whether a batten sits against each end of the wall, and add full-width horizontal rails such as a wainscot top rail. The result lists every batten position, the total linear length and the number of stock lengths to buy.
Shiplap mode handles horizontal boards instead: it counts courses from the coverage width (the exposed face once the laps are nested), gives the rip width of the final course, and offers the alternative of splitting the leftover between the top and bottom courses so neither is a thin strip.
- Battens with end battens = bays + 1; without end battens = bays − 1.
- Clear gap = (wall width − battens × batten width) / bays.
- On-centre spacing = clear gap + batten width.
- Target-gap mode: ideal bays = (wall − batten) / (target gap + batten) with end battens, or (wall + batten) / (target gap + batten) without; the floor and ceiling are compared and the one whose gap is nearer the target wins.
- Battens per stock length = floor((stock + kerf) / (batten length + kerf)); stock for battens = ceil(battens / battens per stock).
- Rails longer than the stock: pieces per rail = ceil(wall / stock). Shorter rails are packed like battens.
- Shiplap courses = ceil(wall height / coverage width); last rip = wall height − (courses − 1) × coverage.
- Balanced rip (top and bottom courses) = (wall height − (courses − 2) × coverage) / 2.
- Stock to buy = ceil(stock before waste × (1 + waste % / 100)).
Worked example
A 3000 mm wall with 70 mm battens and a 400 mm target gap gives an ideal (3000 − 70) / (400 + 70) = 6.23 bays. Six bays give a gap of (3000 − 7 × 70) / 6 = 418.33 mm; seven would give 348.57 mm, which is further from the target, so the layout uses 6 bays and 7 battens at 488.33 mm on centre.
At a 1100 mm wainscot height the battens total 7.7 m, and one full-width top rail adds 3 m. From 2400 mm stock with a 3 mm kerf, 2 battens come from each length, so the battens need 4 lengths and the rail needs 2: 6 before waste and 7 with a 10% allowance.
Shiplap with a 140 mm coverage width on a 2400 mm high wall needs 18 courses. The first 17 cover 2,380 mm, so the last course is ripped to 20 mm — or split the leftover so the top and bottom courses are each 80 mm. On a 3600 mm wall that is 64.8 m of board, or 40 lengths of 3000 mm stock including 10% waste.
Common mistakes
- Marking a fixed spacing from one end, which leaves a narrow panel at the other end.
- Using a nominal batten width (for example 1×4) instead of the measured face width.
- Entering the overall shiplap board width instead of the coverage width left after the laps nest.
- Measuring wall width at floor level only; walls are often wider or narrower higher up.
- Forgetting corner trim, window and door casings that interrupt the layout.
Scope and limits
- One straight, uninterrupted wall. Openings, outlets, stairs and sloped ceilings are not modelled.
- Each vertical batten is one piece; battens are not spliced.
- Horizontal rails and shiplap courses longer than the stock are joined end to end without reusing offcuts, so the count can be slightly high.
- Back panels or sheet material behind the battens are not counted; estimate those with the sheet goods calculator.
- Fixing, adhesive, stud locations, moisture and fire requirements are outside scope.
Common questions
How do I calculate board and batten spacing?
Subtract the total width of all battens from the wall width and divide by the number of bays. With a batten at each end there is one more batten than bays. The calculator chooses the bay count whose gap is closest to your target.
How do I avoid a skinny panel at the end of the wall?
Do not mark a fixed spacing from one corner. Choose a whole number of bays, then calculate the gap from the wall width so every bay is equal. That is exactly what target-gap mode does.
Should there be a batten at each end of the wall?
Usually yes for a framed look. If the wall ends at corner trim, a door casing or an adjoining panelled wall, choose No and the layout starts and finishes with a full gap instead.
What is shiplap coverage width?
It is the face each course adds to the wall once the rebates overlap, plus any spacer gap. It is smaller than the overall board width. Measure two boards nested together or check the supplier's coverage figure.
Does this work in inches?
Yes. Choose Imperial and every length is in inches; results also show the nearest 1/16 in for marking with a tape measure.
Does it account for windows, doors and outlets?
No. It lays out one uninterrupted wall. Lay out walls with openings in sections, or adjust the bay count so battens land on the opening edges.
Sources
- NIST Guide to the SI, Appendix B.8: Factors for units listed alphabeticallyNational Institute of Standards and TechnologyExact inch-to-metre (0.0254) and foot-to-metre (0.3048) factors used for imperial input.