Wall Cladding Calculator

How the wall cladding calculator works

This calculator estimates how many cladding boards, panels or sheets a wall needs. It takes the wall area, adds a wastage allowance for cuts and offcuts, divides by the covering area of one board (its length multiplied by its cover width), and rounds up to whole boards. It also shows an indicative cost from the price per board. The cover width is the visible face once boards are lapped or jointed together, which is a little less than the full board width on shiplap and tongue-and-groove profiles.

Cladding wastage and cutting

The default wastage allowance is 10%. Boards are cut to length at the ends of each run, and the offcut from one row often starts the next, so a staggered layout keeps waste down. Diagonal or herringbone patterns, and walls with many openings, generate more offcut and suit a higher allowance. Tongue-and-groove and shiplap profiles lose a little coverage to the lap, which the cover-width input accounts for.

What this tool does not do

It does not set out the fixing centres, count the battens or fixings, or confirm the cavity and ventilation detail behind the cladding. It does not replace a professional quote, factor regional pricing, or confirm Building Regulations or fire requirements for external cladding. Those remain the responsibility of a suitably qualified designer or your building control officer.

Cover width versus board width

For square-edged boards the cover width equals the board width. For shiplap, tongue-and-groove or overlapping profiles, the cover width is the exposed face after assembly and is the figure to enter — using the full board width would underestimate the number of boards. The product specification lists both dimensions.

On-site considerations

Timber cladding moves with moisture, so boards are often acclimatised before fixing and gapped to allow movement. A single delivery from one batch keeps the grain and colour consistent across a façade, and end cuts are usually sealed on external work.

Adjusting the defaults

Every input here is editable. Enter your own wall area, board length, cover width, wastage allowance and price, and the count and cost recalculate instantly. If a default does not match your boards or wall, your own numbers always take precedence.

Using this wall cladding calculator alongside other BuildMetricLab tools

This calculator works best as part of a wider plan. Pair the board count with our project contingency and labour-cost calculators to build a complete estimate before contacting a supplier. All BuildMetricLab tools run entirely in your browser — no sign-up, no data sent anywhere, and every formula is shown on-page so you can audit the maths.