onlinecalculator.me

Free online square footage calculator

Square footage is the area of a space — how much floor or wall you're covering. This calculator handles rectangles, circles, and triangles, and adds up multiple rooms.

Total area
— sq ft
Square meters
— m²
Square yards
— yd²
About this calculator

How to use

  1. For each room, choose a shape (rectangle, circle, triangle) and unit (ft, in, m, yd).
  2. Enter the dimensions — length/width for rectangles, radius for circles, base/height for triangles.
  3. Press ”+ Add room” to measure additional spaces.
  4. See totals in square feet, square meters, and square yards at the top.

Area formulas

Rectangle:

Area = length × width

Circle:

Area = π × radius²

Triangle:

Area = ½ × base × height

Unit conversions

FromTo sqft
Inchesdivide by 144
Metersmultiply by 10.7639
Yardsmultiply by 9

Worked example

Living room: 15 ft × 12 ft = 180 sqft (16.72 m²)

Dining room (rectangular nook): 8 ft × 10 ft = 80 sqft (7.43 m²)

Total: 260 sqft (24.15 m²)

Add 10% for flooring waste → order ≈ 286 sqft of material.

Notes

  • 1 ft² = 0.09290304 m² (exact, NIST definition).
  • 1 acre = 43,560 ft².
  • The calculator shows acres for reference when total area is large.

Frequently asked

How do I calculate square footage of a rectangular room?
Area (sqft) = length (ft) × width (ft). If you have measurements in inches, the calculator converts automatically (1 ft = 12 in, so 1 ft² = 144 in²). For meters, 1 m² = 10.7639 ft².
How do I calculate square footage of a circular room?
Area (sqft) = π × radius² (in feet). For a round room with a 10 ft diameter, radius = 5 ft: π × 25 ≈ 78.54 sqft.
How do I calculate square footage of a triangular room or nook?
Area = ½ × base × height (in the same unit). Example: base 10 ft, height 8 ft → 0.5 × 10 × 8 = 40 sqft.
Can I calculate multiple rooms?
Yes. Press "+ Add room" to add as many rooms as you need. The total at the top is the combined square footage. A per-room breakdown appears when you have more than one room.
How much flooring do I need?
Add 10–15% to the total square footage for waste and cuts, especially with tile, hardwood, or diagonal layouts. The calculator gives you the pure area; add your waste factor separately.