Square Footage Calculator

Formula and worked example

Convert each length and width to one common linear unit, multiply each rectangle, then add the areas. Square-foot conversion uses squared—not linear—conversion factors.

A 12 ft by 15 ft rectangle contains 180 ft². Two sections measuring 10 ft by 10 ft and 5 ft by 10 ft total 150 ft².

Calculations retain floating-point precision and use controlled display formatting. Decimal results involving π are approximations.

Square footage versus general area

This page focuses on practical rectangular measurements reported primarily in square feet.

Use Area Calculator for circles, triangles, trapezoids, and other geometric shapes.

The result is area only; it does not estimate flooring, paint, concrete, asphalt, soil, or another material quantity.

Measuring multiple sections

Divide an irregular outline into non-overlapping rectangles.

Measure each section consistently and add it as a separate row.

Avoid counting overlapping space twice.

The calculator supports up to 25 sections to keep the form manageable.

Units and limits

Each dimension has its own explicit unit selector.

One foot equals 12 inches, but one square foot equals 144 square inches.

Zero dimensions produce zero area; negative or nonfinite dimensions are rejected.

Methodology and limits

Formulas are standard Euclidean geometry. Length conversions follow exact defined factors, including 1 inch = 0.0254 meter; area factors are squared and volume factors are cubed. This browser-local tool does not evaluate expressions or infer real-world material needs.