# 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.

Calculate the square footage of one or more rooms in rectangle, circle, or triangle shapes. Supports feet, inches, meters, and yards with totals in all four unit systems.

**Interactive version:** https://onlinecalculator.me/construction/square-footage/
**Category:** Construction

## 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

| From | To sqft |
|---|---|
| Inches | divide by 144 |
| Meters | multiply by 10.7639 |
| Yards | multiply 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 questions

### 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.

## Sources

- [Square foot — unit of area](https://en.wikipedia.org/wiki/Square_foot) — Wikipedia
- [Area — formulas for rectangles and other shapes](https://en.wikipedia.org/wiki/Area) — Wikipedia

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