Geometry
Square Footage Calculator
Find the area of any room or space — rectangle, round, triangle, or a whole multi-room layout. Mix feet, inches, yards, or meters per field; get square feet, m², yd², and acres, plus waste and material cost, updating as you type.
Measurements
Material estimate (optional)
Total area
120.00
12.00 ft × 10.00 ft
m²
11.15
yd²
13.33
acres
0.0028
Buy with 10.00% waste
132.00 ft²
Try an example
No sign-up · Free
The basics
What is square footage?
Square footage is the area of a flat surface measured in square feet — the count of one-foot-by-one-foot tiles that would cover it. It is the standard way to size rooms, floors, walls, lawns, and lots in the US, and it always comes from multiplying two lengths together.
Area = length × width
It is two lengths multiplied
A length on its own is a single distance. Multiply a length by a width and you get an area — a flat surface — which is why the unit is written ft² or “square feet.”
12 ft × 10 ft = 120 ft²
same unit on both sides
Units must match before you multiply
You cannot multiply feet by inches and get a sensible area. Convert both measurements to the same unit first — the tool above normalizes every field to feet for you.
120 in ÷ 12 = 10 ft, then × width
Method
How to calculate square footage by hand
Four steps cover every rectangular room, and the same idea extends to other shapes.
- 1
Measure length and width
Measure the space wall to wall along two perpendicular sides. Use a tape measure and write both numbers down in the same unit.
length = 12 ft width = 10 ft - 2
Put both in the same unit
Area only works when both sides share a unit. Convert inches to feet (÷ 12), yards to feet (× 3), or meters to feet (× 3.28) first.
120 in ÷ 12 = 10 ft - 3
Multiply length by width
The product is the area in square feet — the number of one-foot squares that fit inside the space.
12 ft × 10 ft = 120 ft² - 4
Add rooms or convert as needed
For multiple or L-shaped areas, square-foot each rectangle and add them. To convert, divide ft² by 10.7639 for m², or by 9 for yd².
120 ft² ÷ 10.7639 ≈ 11.15 m²
Shape formulas
Square footage of any shape
Most spaces are rectangles, but the calculator handles the other common floor plans too. Here is the formula behind each mode.
A = l × w
Rectangle & square
Length times width. A square is just a rectangle where both sides are equal, so the same formula applies.
16 × 14 = 224 ft²
A = π × r²
Circle / round room
Halve the diameter to get the radius r, square it, and multiply by π. Good for round patios, gazebos, and silos.
r = 7 → π × 49 ≈ 153.9 ft²
A = ½ × b × h
Triangle
Half the base times the perpendicular height. Useful for gable walls, corner lots, and triangular nooks.
½ × 16 × 9 = 72 ft²
A = ΣA = A₁ + A₂ + …
L-shaped & multi-room
Split an irregular space into rectangles, find each area, and add them. Multi-room mode keeps a running total for you.
192 + 48 = 240 ft²
Worked examples
See it across shapes
The same area idea, worked end to end for the four shapes the tool supports.
Given A bedroom 12 ft long and 10 ft wide
Formula Area = length × width
Area = 12 ft × 10 ft
Area = 120 ft²
Area = 120.00 ft²
Quick chart
How many square feet is X by Y?
Pick a room length and read the square footage for every common width — the fast answer to “how big is a 12×14 room?” without doing the arithmetic.
Room length (ft)All measurements in feet
12 × 8 ft
96.00 ft²
12 × 9 ft
108.00 ft²
12 × 10 ft
120.00 ft²
12 × 11 ft
132.00 ft²
12 × 12 ft
144.00 ft²
12 × 13 ft
156.00 ft²
12 × 14 ft
168.00 ft²
12 × 15 ft
180.00 ft²
12 × 16 ft
192.00 ft²
12 × 18 ft
216.00 ft²
12 × 20 ft
240.00 ft²
12 × 24 ft
288.00 ft²
Reference
Square feet to m², yd², and acres
Convert any area between the units people actually use — square meters for metric specs, square yards for carpet, and acres for land.
m²
46.45
yd²
55.56
acres
0.01
| Square feet | Square meters | Square yards | Acres |
|---|---|---|---|
| 50.00 | 4.65 | 5.56 | 0.0011 |
| 100.00 | 9.29 | 11.11 | 0.0023 |
| 150.00 | 13.94 | 16.67 | 0.0034 |
| 200.00 | 18.58 | 22.22 | 0.0046 |
| 250.00 | 23.23 | 27.78 | 0.0057 |
| 300.00 | 27.87 | 33.33 | 0.0069 |
| 400.00 | 37.16 | 44.44 | 0.0092 |
| 500.00 | 46.45 | 55.56 | 0.01 |
| 750.00 | 69.68 | 83.33 | 0.02 |
| 1,000 | 92.90 | 111.11 | 0.02 |
| 1,500 | 139.35 | 166.67 | 0.03 |
| 2,000 | 185.81 | 222.22 | 0.05 |
Where it shows up
What square footage is used for
The single number behind most home, real-estate, and renovation decisions.
ft² × price/ft²
Flooring & tile
Carpet, hardwood, laminate, and tile are all priced by the square foot. Area times price (plus waste) is your material cost.
area ÷ 350–400
Paint
A gallon of paint covers roughly 350–400 square feet per coat. Divide the wall area by that to size the job.
price ÷ ft²
Real estate
Homes and rentals are compared on price per square foot, so the area sets the listing and the value.
Worth knowing
Tips and common mistakes
The small things that throw a square-footage estimate off — and how to avoid them.
ft² ≠ ft
Don't confuse area with length
Doubling a room's side doesn't double its area — it quadruples it. Area grows with the square of length, so always multiply two dimensions.
measure wall to wall
Measure the full footprint
Measure baseboard to baseboard, not just the open floor. Closets and alcoves count, and missing them undercounts the area.
split irregular shapes
Break odd rooms into rectangles
Any L, T, or U shape is just rectangles stuck together. Divide on paper, area each piece, and add — the Multi-room mode does the adding.
add 10–20% waste
Buy more than the bare area
Cuts, breakage, and pattern matching waste material. Add 10% for simple layouts and up to 20% for diagonal or patterned installs.
round the diameter, not π
Circles use the radius
For round spaces, halve the diameter first. Squaring the radius — not the diameter — is the most common slip.
1 m² = 10.7639 ft²
Keep the conversion factor handy
Metric plans give meters. One square meter is about 10.76 square feet, so a small-sounding figure in m² is larger in ft² than people expect.
FAQ
Common questions
Measure the length and the width of the space in feet, then multiply them together: square footage = length × width. A room 12 feet long and 10 feet wide is 12 × 10 = 120 square feet. If your measurements are in inches, yards, or meters, convert them to feet first so both sides use the same unit.
For a rectangular room, multiply its length by its width in feet. For an L-shaped or irregular room, split it into rectangles, find the square footage of each, and add them together. Always measure wall to wall and keep both measurements in the same unit before multiplying — the Multi-room mode above does this addition for you.
A 12 by 12 foot room is 12 × 12 = 144 square feet. The same method works for any rectangle: 10×10 is 100 sq ft, 12×16 is 192 sq ft, and 20×20 is 400 sq ft. The Quick Chart above lists dozens of common room sizes at a glance.
Divide the square footage by 10.7639, because one square meter equals 10.7639 square feet. For example, 120 square feet ÷ 10.7639 ≈ 11.15 square meters. To go the other way, multiply square meters by 10.7639.
Measure the diameter straight across the widest point, halve it to get the radius, then use Area = π × radius². A round patio 14 feet across has a 7-foot radius, so its area is π × 7² ≈ 153.9 square feet. Switch the tool to Round mode and it does this for you.
Add roughly 10% to your square footage for straight, simple rooms, and 15–20% for diagonal layouts, patterned tile, or rooms with lots of cuts and angles. The waste field above bumps the figure for you so the cost estimate reflects what you actually need to purchase.
Flooring is sold by the square foot, so multiply the area (plus waste) by the price per square foot. For paint, divide the wall area by the coverage of a gallon — about 350–400 square feet per coat — and round up. Entering a price per square foot above gives you the material cost directly.
Feet measure length — a single, straight distance. Square feet measure area — the amount of flat surface inside a boundary. You get square feet by multiplying two lengths (length × width), which is why the unit is written ft² or 'square feet'.
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Ugo CharlesBuilt and fact-checked against our editorial standards · Last updated June 2026
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