Square Footage Calculator
A square footage calculator works out the area of a surface in square feet based on its shape and dimensions. Use it to measure rooms before buying flooring or carpet, plan a deck or patio, figure out how much paint you need, or estimate material quantities for any construction or home improvement project. Supports rectangles, circles, and triangles — the most common shapes you will encounter indoors and outdoors.
Quick answer
The result shows the total area of your surface in square feet (ft²).
What this tells you
- •The result shows the total area of your surface in square feet (ft²).
- •All inputs must be in feet — convert inches by dividing by 12.
- •For irregular shapes, calculate each section separately and add the areas together.
How to Use
- 1Select the shape that best matches your surface — rectangle, circle, or triangle
- 2Enter the required measurements in feet (decimals are supported, e.g. 10.5)
- 3Click Calculate to see the total square footage
- 4Use the Reset button to clear all fields and start a new calculation
How It Works
Formula
Rectangle: Area = Length × Width
Circle: Area = π × Radius²
Triangle: Area = (Base × Height) ÷ 2All measurements must be in feet. For the circle, enter the radius (half the diameter). For triangles, the height is the perpendicular distance from the base to the opposite vertex, not the length of a side. The result is in square feet (ft²).
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
Rectangular bedroom
A standard bedroom measuring 14 feet by 12 feet has an area of 14 × 12 = 168 square feet. This is the figure used when ordering flooring or carpet.
Circular patio
A circular patio with an 8-foot radius covers π × 8² ≈ 201.06 square feet. Remember: radius is half the width of the circle, not the full width.
Triangular garden bed
A triangular garden bed with a 10-foot base and 7-foot perpendicular height covers (10 × 7) ÷ 2 = 35 square feet.
Common mistakes
- Entering diameter instead of radius for circles (the radius is half the diameter)
- Measuring the slant height of a triangle instead of the perpendicular height
- Mixing units — all values must be in feet before calculating
- Forgetting to convert inches to feet (divide inches by 12 first)
- Calculating only one room section when the full floor plan has an irregular shape that should be split into multiple shapes