Square Footage Calculator
Calculate area in square feet for rooms and common shapes.
100% freeNo sign-up No data leaves your browserPrivacy
This square footage calculator finds the area of a space in square feet, then converts it to square metres, square yards, and acres. Pick a shape — rectangle, circle, triangle, or trapezoid — and enter the dimensions in feet.
Measuring a whole home or several rooms? Switch to Room mode to add each room and get the combined total — handy for flooring, paint, or working out a price per square foot. Everything calculates instantly in your browser.
Formula
Rectangle / room
area = length × width
The most common case. A 10 ft × 12 ft room is 120 square feet. Add rooms together for a total.
Circle
area = π × radius²
Use the radius (half the diameter). A circle of radius 5 ft is π × 25 ≈ 78.54 sq ft.
Triangle & trapezoid
triangle = ½ × base × height; trapezoid = ½ × (a + b) × height
For a trapezoid, a and b are the two parallel sides and height is the perpendicular distance between them.
Unit conversions
1 ft² = 0.0929 m² = 1/9 yd²; 1 acre = 43,560 ft²
The calculator shows all four units so you can use whichever the job needs.
Examples
| Example | Input | Result |
|---|---|---|
| Rectangle | 10 ft × 12 ft | 120 ft² (11.15 m²) |
| Circle | radius 5 ft | 78.54 ft² |
| Two rooms | 10×12 + 8×10 | 200 ft² |
How to use the square footage calculator
- 1Choose Single shape or Multiple rooms.
- 2For a single shape, pick the shape and enter its dimensions in feet.
- 3For rooms, enter each room's length and width and add as many as you need — the total updates automatically.
- 4Read the area in square feet, square metres, square yards, and acres.
How to calculate square footage
For a rectangular room, square footage is simply length times width, both measured in feet. A room 12 feet long and 10 feet wide is 120 square feet. For an L-shaped or irregular space, the trick is to split it into rectangles, work out each one, and add them up — exactly what Room mode does for you. Round measurements to the nearest few inches (in decimal feet) for a close estimate; for materials, measure to the inch.
Other shapes have their own formulas: a circle is π times the radius squared, a triangle is half the base times the height, and a trapezoid is half the sum of its two parallel sides times the height. This calculator handles all four so you don't have to remember them.
Square feet, metres, yards, and acres
Different jobs use different units. Flooring and paint are usually priced per square foot or square metre; carpet is often sold by the square yard; and land is measured in acres. One square foot is about 0.0929 square metres, there are nine square feet in a square yard, and an acre is 43,560 square feet. The calculator shows every unit at once, so converting is one less thing to think about.
If you need to convert other measurements — feet to metres, or inches to centimetres — the [Unit Converter](/tools/unit-converter) handles length, weight, temperature, and more.
Buying flooring, paint, or carpet
Once you know the area, always add a waste allowance before ordering. For flooring, a common rule is to add 5–10% for cuts and mistakes (more for diagonal or patterned layouts). For paint, divide your wall area by the coverage on the tin (often around 350–400 sq ft per gallon) and remember most walls need two coats. Measuring carefully and adding a margin is far cheaper than a second trip to the store mid-project.
For pricing, divide the total cost by the square footage to compare options on a like-for-like basis — a quick use of the [Percentage Calculator](/tools/percentage-calculator) can help if there's a discount involved.
Results are only as accurate as your measurements. For flooring, paint, or material orders, measure carefully and add a waste allowance before purchasing.
Frequently asked questions
How do I calculate the square footage of a room?
Multiply the room's length by its width, both in feet. A 10 ft × 12 ft room is 120 square feet. For multiple or L-shaped rooms, split them into rectangles, calculate each, and add the totals — Room mode does this for you.
How many square feet are in a square metre?
About 10.76 square feet. Conversely, one square foot is roughly 0.0929 square metres. The calculator shows both automatically.
How do I find the square footage of a circle?
Use π × radius². Measure the radius (half the width) in feet, square it, and multiply by π (≈ 3.1416). A 5-foot radius gives about 78.54 square feet.
How much extra should I buy for flooring?
Add about 5–10% to your measured area for cuts and waste — more for diagonal or patterned installations. Always round up when ordering.
Embed this calculator
Add the Square Footage Calculator to your own website — free. Copy and paste this snippet:
<iframe src="https://numvella.com/embed/square-footage-calculator" width="100%" height="460" style="border:1px solid #e2e8f0;border-radius:12px" title="Square Footage Calculator — Numvella" loading="lazy"></iframe>