chuck How the calculation works
Net area = length × width − excluded area. Planned coverage = net area × (1 + allowance ÷ 100). Packs = planned coverage ÷ coverage per pack, rounded up. Surplus = purchased coverage − planned coverage.
Use the result with care
A zero allowance is just the starting input, not a recommendation. Use effective installed coverage, including any product-specific overlaps or joint assumptions. Whole-area arithmetic does not plan tile patterns, board orientation, sheet cuts or usable offcuts. Multiple coats and layers need to be included in your coverage basis before using the result.
Your figures stay in this page
The calculation runs in your browser. These entries are not sent to a calculator service or saved by this tool. Reset returns the form to its starting values.