Guide
How to measure a room before buying materials
A practical guide to getting room area right the first time, avoiding common measurement mistakes, and buying the right amount of flooring, paint, or carpet.
Start with the longest walls
For a rectangular room, measure the full length and full width. Multiply them together for the floor area. Use the same unit throughout — mixing metres and feet is the most common source of wrong results.
Awkward rooms need breaking down
L-shapes, alcoves, bay windows, and chimney breasts change the effective area. Break the room into rectangles, calculate each one separately, and add or subtract them. The Room Area Tool handles the maths once you have the dimensions.
Add a waste allowance before you buy
Flooring and carpet suppliers typically recommend a 10–15% waste allowance for cuts, direction changes, and pattern matching. Paint coverage depends on the wall height, number of coats, and surface porosity. Use the calculated area as a starting point, not a finished order quantity.