Free carpet calculator estimates carpet area, roll length and total cost for any room, with waste allowance for cuts and joins.
Carpet is sold by the square meter but laid from a roll, which is why simple area math never matches the bill. The roll is a fixed width (usually 12 ft or 3.66 m), so the number that matters is the roll length the installer has to cut - and that depends on how the room fits across the roll.
Enter your room dimensions, the roll width and a waste allowance. The calculator returns the carpet area to buy, the roll length needed and an estimated cost.
Most residential carpet comes in 12 ft (3.66 m) rolls; 13.5 ft (4.11 m) rolls exist for larger rooms. If your room is wider than the roll, the installer needs extra length to seam strips together - the calculator accounts for this with the roll width input.
A 10% allowance is typical for straight installations. Patterned carpet needs 15-20% extra so the installer can match the pattern across seams. Stairs and irregular shapes also add waste - treat the calculator result as a starting point.
Stairs need the tread depth plus riser height for each step, multiplied by the stair width. Measure one step (tread + riser), multiply by the number of steps, and add the same waste allowance. Run this calculation separately from the room area.