Square Footage Calculator
It calculates the area of a rectangle, circle, triangle or trapezoid and converts the result to square feet, inches, yards, meters and acres.
Total area
120.00 ft²
Square feet
120.00
Square meters
11.15
Square yards
13.33
Square inches
17,280
Acres
0.0028
+10% waste
132.00 ft²
What it calculates
It calculates the area of a rectangle, circle, triangle or trapezoid and converts the result to square feet, inches, yards, meters and acres.
Why it matters
Flooring, paint, turf, tiling and land are all priced by area, and quoting the wrong figure means paying for the wrong quantity of material.
Who it's for
Homeowners planning a renovation, contractors quoting a job, landscapers, and anyone buying flooring or land.
Formula
- A
- Area in the square of the entered unit
- r
- Radius, for circles
- h
- Height, for triangles and trapezoids
Worked example
A room 12 ft by 10 ft
- 1Area = length × width
- 212 × 10 = 120
120 sq ft, which is 13.33 sq yd or 11.15 m²
How the square footage calculator works
A rectangle is length times width. A circle is πr². A triangle is half the base times the height. A trapezoid averages the two parallel sides and multiplies by the height between them. For an irregular room, split it into rectangles, calculate each and add them — that is how contractors measure in practice.
For an irregular room, split it into rectangles, calculate each one and add them together — that is how contractors measure in practice, and it is far more accurate than averaging dimensions.
Remember that a circle's formula takes the radius, not the diameter. Using the diameter by mistake quadruples the area.
Common mistakes
- Using a circle's diameter where the formula wants the radius, which quadruples the area.
- Measuring a triangle's sloped side instead of its perpendicular height.
- Forgetting a waste allowance — flooring and tile need 5–10% extra for cuts.
Tips and best practice
- Break irregular rooms into rectangles and sum them rather than averaging dimensions.
- Add 10% for material with a pattern that has to line up.
Frequently asked questions
How do I calculate square footage?
For a rectangular room, multiply length by width in feet. A 12 ft by 10 ft room is 120 square feet.
How many square feet are in a square meter?
One square meter is 10.764 square feet. Going the other way, one square foot is 0.0929 square meters.
How do I measure an irregular room?
Split it into rectangles, calculate each area separately, and add them together. Alcoves and bays are usually easiest handled as separate rectangles.
How many square feet are in an acre?
43,560 square feet, which is about 4,047 square meters or 0.405 hectares.
Should I add extra for waste?
Yes — typically 5–10% for plain flooring and tile, and up to 15% for patterned material or diagonal layouts.
Related calculators
Methodology & trust
- Formula source
- Standard plane geometry with exact unit conversions.
- Last updated
- 2026-07-28
- Privacy
- Every calculation runs in your browser. No inputs are sent to a server or stored.
- Accessibility
- Keyboard navigable, labeled inputs and WCAG AA color contrast.