Room Measurements Calculator
Add each rectangular room with its length, width and height to see floor area, perimeter, wall area and volume, per room and in total.
The allowance adds the percentage you enter to the floor and net wall areas: adjusted area = area × (1 + allowance ÷ 100). Leave it blank for no allowance.
Result
Enter the length, width and height of each room to see floor area, perimeter, wall area and volume, per room and in total. Add openings such as doors and windows to subtract them from the wall area.
How the Calculation Works
Each room is treated as a rectangle. Floor area = length × width. Perimeter = 2 × (length + width). Gross wall area = perimeter × height. Volume = length × width × height.
Openings you enter, such as doors and windows, are subtracted from the gross wall area. Openings larger than the wall area are rejected. The material allowance adds the percentage you enter to the floor and net wall areas: adjusted area = area × (1 + allowance ÷ 100).
Worked example: a room 20 ft long, 15 ft wide and 8 ft high has 300 ft² of floor, 70 ft of perimeter, 560 ft² of wall area and 2,400 ft³ of volume, before openings.
About the Numbers You Enter
Measure each room yourself and enter the figures here. Switching between Imperial and Metric converts the numbers you already entered without rounding drift.
This tool only does the arithmetic on the numbers you enter. It does not size equipment, recommend materials or judge whether a space meets any requirement.