Estimate the square footage of a lot, room, or other surface from a common shape. Pick a tab, enter lengths in feet, yards, inches, miles, meters, kilometers, or centimeters, and optionally a unit price. Complex outlines can be split into these shapes and added together.
Area conversion factors
Factors use the international foot (1 ft = 0.3048 m exactly) and 1 acre = 43,560 ft², consistent with NIST conversion tables.
| Unit | Square feet |
|---|---|
| 1 acre | 43,560 ft² |
| 1 square yard | 9 ft² |
| 1 square meter | 10.76391041671 ft² |
| 1 square inch | 1/144 ft² |
| 1 square centimeter | 0.001076391041671 ft² |
Examples
30 ft by 20 ft rectangle
Length 30 ft and width 20 ft is 600 ft². At quantity 1 the result is labeled Area. Two 10 ft by 12 ft rectangles at $3 per square foot are 240 ft² and $720.
Rectangle border and ring
A 30 ft by 20 ft rectangle with a 2 ft border is 600 − 26 × 16 = 184 ft². A 30 ft diameter circle with a 2 ft ring is π(15² − 13²) = 175.92918860103 ft².
Circle, triangle, and sector
A 30 ft diameter circle is 706.8583470577 ft². A 3-4-5 triangle counted twice at $3/ft² is 12 ft² and $36. A 10 ft radius sector of 45°, quantity 2, at $3/ft² is 78.539816339745 ft² and $235.62.
1 m by 1 m at $10 per square meter
Each side is 1 / 0.3048 feet, so the area is 10.76391041671 ft². Converted back to square meters that is exactly 1 m², so the price is $10.
Formula
All lengths are converted to feet, the area of one shape is computed in square feet, then multiplied by quantity. Cost (when a price is entered) converts that area into the price unit and multiplies.
area_ft² = shape area in feet × quantity
price = round to cents(area in price unit × unit price)
Rectangle, parallelogram, triangle (base and height), trapezoid, and circular shapes:
rectangle = L × W
rectangle border = L × W − max(0, L − 2b) × max(0, W − 2b)
circle = π × (D / 2)²
ring = π/4 × (D² − d²) d = max(0, D − 2b)
triangle (b,h) = (b × h) / 2
trapezoid = ((b1 + b2) / 2) × h
sector = (θ / 360) × π × r² (θ in degrees)
= (θ / 2) × r² (θ in radians)
parallelogram = b × h
Three-sided triangles use Heron's formula:
s = (a + b + c) / 2
area = √(s(s − a)(s − b)(s − c))
Before buying materials
Square footage is a horizontal or planar geometry result. It does not include slope, curved-surface area, openings, offcuts, pattern matching, damaged pieces, or package rounding. The optional price is the area multiplied by the price you enter; it excludes tax, delivery, labor, and any supplier minimum. Measure the same finished or rough surface that the product specification uses, then use the related material calculator to add the relevant waste and package rules.
Turn floor area into a project estimate
For a roof, a flat footprint is only the starting point: the Roofing Calculator accounts for pitch and eaves. For a slab, the Concrete Calculator adds thickness to convert area into volume. Keep those project dimensions separate from the floor-area measurement.
Compare property prices and rental quotes
Once the floor area is known, use the price per square foot calculator to divide a total price by area or work backward from a quoted rate. It distinguishes monthly rent from annual lease quotes and calculates an area-weighted price when comparing several properties.
Turn a floor measurement into a purchase
The measured floor area is only the starting point for a boxed-flooring order. The Flooring Calculator subtracts exclusions, adds your waste allowance, rounds up to complete boxes and separates material cost from installed-area labor. Use one combined order only when rooms share the same product.