Square Feet of a Rectangle Calculator
Find the square footage of any rectangular room, floor, wall, or land plot. Enter the length and width in feet, inches, yards, metres, centimetres, or millimetres — the calculator converts everything to square feet and also shows square metres and acres.
Unit of measurement
Length × Width converted to square feet
- 1
Length
20 ft - 2
Width
15 ft - 3
Area
20 × 15 = 300Area equals length multiplied by width, both in feet.
How does this calculator work?
Multiply length × width (both in feet) to get the area in square feet. Enter dimensions in any unit (ft, in, yd, m, cm, mm) and the calculator converts everything automatically, showing sq ft, m², and acres side by side.
Formula
How this is calculated
The area of a rectangle is simply its length multiplied by its width. The key step when the dimensions are given in non-foot units is converting each measurement to feet first, then multiplying: for example, 120 inches × 96 inches → 10 ft × 8 ft = 80 sq ft.
The calculator accepts six units (feet, inches, yards, metres, centimetres, millimetres) and converts each dimension to feet using the exact factor 1 ft = 0.3048 m before computing the area. It also converts the resulting square footage to square metres (×0.09290304) and acres (÷43 560) for quick reference.
For rooms with walls that are not perpendicular, or spaces with alcoves, measure each rectangular section separately and add the areas. The diagonal shown is derived from the Pythagorean theorem and is useful for checking that corners are square.
Frequently asked questions
Measure the length and width of the room in feet, then multiply: Area = Length × Width. For a room 12 ft × 10 ft the area is 120 sq ft. If your measurements are in other units, convert to feet first (1 yard = 3 ft, 1 inch = 1/12 ft, 1 metre ≈ 3.2808 ft).
Only for rectangular (four right-angle) rooms. For L-shaped or other irregular rooms, divide the space into rectangles, calculate each area separately, and add them together.
Linear feet measure a single dimension (length). Square feet measure area — it is the product of two linear dimensions. A room 10 linear feet by 12 linear feet has 120 square feet of area.
Also known as
TG we-Calculate Editorial Team. (2026). Square Feet of a Rectangle Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/square-feet-of-rectangle-calculator
TG we-Calculate Editorial Team. "Square Feet of a Rectangle Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/square-feet-of-rectangle-calculator.
TG we-Calculate Editorial Team, "Square Feet of a Rectangle Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/square-feet-of-rectangle-calculator
@misc{wecalculate_square_feet_of_rectangle_calculator, title = {Square Feet of a Rectangle Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/square-feet-of-rectangle-calculator}}, year = {2026}, note = {TG we-Calculate} }
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