Why use a calculator before you shop?
Buying too little means a second trip to the store and – for paint and tile – a risk that the next batch won't match. Buying too much wastes money on material you can't return. These calculators use the same rules of thumb contractors use, including a sensible waste allowance, so you can buy the right amount the first time.
Every tool works in both imperial (feet, inches, gallons) and metric (meters, centimeters, liters). Your choice is remembered across the site.