Category
Interior Finishes calculators
Quick take-offs for the work that happens once the structure is closed in. Enter room dimensions once and get gallons of paint, sheets of drywall or square footage of flooring — with door and window deductions and a waste factor that matches industry practice.
All Interior Finishes calculators
Wall area, deductions and waste
Every interior take-off starts with the same geometry: 2 × (L + W) × H
for the four walls of a room, plus L × W if you are also covering the
ceiling. From that gross area we deduct a fixed allowance for each door (20 – 21 ft²)
and window (15 ft²), then apply a waste factor — paint adds nothing for re-coats,
drywall adds 8 – 10 % for cut waste, tile adds 10 – 15 % depending on pattern.
Coverage rates and yields
Each finish has its own conversion from square footage to product. Paint covers 350 ft² per gallon (9 m² per litre) at one coat; drywall comes in 4×8, 4×10 or 4×12 sheets that yield 32, 40 or 48 ft²; tile is sold by the box with a stated square-foot coverage. Our calculators apply the right yield for each material so you don’t have to convert by hand.
Optional cost — your prices, in your browser
Every calculator has an optional price field. Leaving it blank gives a pure material quantity; filling it in multiplies by your unit price for an indicative total. Prices stay in your browser and are never transmitted.