How to use the square footage calculator
Pick your shape from the dropdown — most rooms are a plain Rectangle, but if you're pricing a circular patio, a triangular gable end, an L-shaped border, or a wall with a window cut out of it, there's a mode for that too. Enter the dimensions and watch the live diagram below the result redraw with your actual numbers as you type. Add the area to your project total and repeat for every room or section — the running total sums everything for you, with an optional waste buffer and an instant cost estimate.
The basic formula
A rectangle is simply length times width. A circle is π times the radius squared. A triangle is half the base times the height. Every shape mode above works out the correct formula for you — you just need to measure the right dimensions.
Splitting an irregular room into simple shapes
Most real rooms aren't perfect rectangles. The standard approach is to mentally split the space into rectangles, circles or triangles that don't overlap, work out each section's area, then add them together. That's exactly what the project total does automatically — measure each section, add it, and move to the next one. An L-shaped room, for example, is just two rectangles added together.
Worked example
A rectangular bedroom 14 ft long and 11 ft wide, plus a closet alcove 3 ft by 4 ft:
14 × 11 = 154 sq ft. 3 × 4 = 12 sq ft. Added together: 166 sq ft total.
Square feet, square yards and acres
Results convert automatically: 9 sq ft = 1 sq yd, and 43,560 sq ft = 1 acre. In metric, 10,000 m² = 1 hectare. The subtitle under every result shows the equivalent so you don't need a separate converter.
| Unit | Equals |
|---|---|
| 1 square yard | 9 sq ft |
| 1 acre | 43,560 sq ft |
| 1 hectare | 10,000 m² |
| 1 square metre | ≈10.76 sq ft |
How much extra for waste?
- 5–10% — a simple rectangular layout
- 10–15% — rooms with lots of corners or angles
- 15%+ — diagonal, herringbone or chevron patterns
Tap “+ Add waste calc” in the project total to add a percentage buffer on top of your measured area.
Pricing your project
Enter a price per unit area and every area you add gets priced automatically, with a running project cost at the bottom. Pair this with the Flooring Calculator once you know the square footage and want an exact box count, or the Tile Calculator for individual tile counts.
Common questions
How do I calculate square footage?
For a rectangular room, multiply the length by the width in feet. For an irregular space, split it into simple shapes — rectangles, circles, triangles — calculate each one and add them together. This calculator does that automatically: add each shape to the project total and it sums the whole area for you.
How do I find the square footage of a circular area?
Measure the diameter, divide it by 2 to get the radius, then use Area = π × radius². Enter the diameter in the Circle mode above and it's calculated instantly.
How do I calculate the area of an L-shaped or irregular room?
Break the room into rectangles (or other simple shapes) that don't overlap, calculate each section's area separately, then add them together. Add each section to the project total above and the running total does the adding for you.
How many square feet are in an acre?
One acre is 43,560 square feet. This calculator shows the acre equivalent automatically underneath any US-units result once the area is large enough to matter.
How much extra should I buy for material waste?
For straightforward rectangular layouts, 5–10% extra covers cuts and offcuts. For rooms with lots of angles, or diagonal/herringbone patterns, 10–15% is safer. Use the “+ Add waste calc” option in the project total to add a percentage buffer to your order.