A rectangular bedroom
- Input
- Rectangle: Length = 12 ft, Width = 10 ft
- Working
- Area = 12 × 10 = 120 ft².
- Result
- Area = 120 ft²
Square Footage Calculator
Calculate the area of rectangles, circles and triangles and add them into one total — the starting figure for paint, tile, flooring and garden materials. Runs entirely in your browser — your numbers never leave this device.
Unit
Shape
Room 1: 120 ft²
Total area (ft²)
120
= 11.15 m²
- Number of areas
- 1
- Largest single area
- 120 ft²
Circle areas use the full diameter (π × (d/2)²) and triangle areas use ½ × base × height. Break irregular rooms into rectangles and add them as separate rows.
How it works
Rectangle: area = length × width | Circle: area = π × (diameter ÷ 2)^2 | Triangle: area = base × height ÷ 2 | Total = sum of all areas
| Shape | Area formula |
|---|---|
| Rectangle | Length × width |
| Circle | π × radius^2 |
| Triangle | Base × height ÷ 2 |
| Trapezoid | (a + b) ÷ 2 × height |
Most rooms and plots are one rectangle, but real spaces are combinations: an L-shaped room is two rectangles, a round patio is a circle, a gable end is a triangle. This builder calculates each shape with its standard area formula and adds the results into a single total, so a composite space is measured shape by shape rather than guessed as one figure. The reference table also lists the trapezoid formula for spaces with two parallel sides of different lengths.
That total is the figure the rest of this category hangs off. Paint, tile, flooring, mulch and gravel all start from an area — wall area for paint, floor area for tile and flooring, bed area for mulch and gravel — so an error here multiplies through every material estimate that follows. Measuring each dimension twice and entering shapes separately when a room is not a clean rectangle is what keeps the downstream numbers honest.
Areas are reported in square feet and square metres with the conversion applied at full precision: the metric worked example converts 12 m² to 129.2 ft². Like every tool here, the calculation runs in the browser and nothing entered is stored.
Worked examples
Three shapes combined
- Input
- Rectangle 12 × 10 ft, Circle diameter 10 ft, Triangle base 8 ft × height 6 ft
- Working
- Rectangle = 120 ft². Circle = π × (10 ÷ 2)^2 = π × 25 = 78.5 ft². Triangle = 8 × 6 ÷ 2 = 24 ft². Total = 120 + 78.5 + 24 = 222.5 ft².
- Result
- Total area = 222.5 ft²
A metric room, converted
- Input
- Rectangle: Length = 4 m, Width = 3 m
- Working
- Area = 4 × 3 = 12 m². Converted: 12 m² = 129.2 ft².
- Result
- Area = 12 m² (129.2 ft²)
Frequently asked questions
How are irregular rooms handled?
By splitting them into the shapes in the builder. An L-shaped room becomes two rectangles; a bay adds a triangle or trapezoid section. Each shape is calculated with its own formula and the areas are summed, which is more accurate than treating the whole space as its bounding rectangle.
Why is the trapezoid formula listed if the builder covers three shapes?
As a printed reference for hand calculations — the builder covers rectangle, circle and triangle, and the table carries the trapezoid form, (a + b) ÷ 2 × height, alongside them so a tapered space can still be worked out from the page.
Which area do paint and flooring need?
Different ones. Flooring and tile use floor area; paint uses wall area — perimeter times ceiling height, minus doors and windows — which the Paint Calculator builds from room dimensions directly. This page supplies the floor and surface areas the other tools start from.
How are square metres converted to square feet?
By the exact area relationship derived from 1 ft = 0.3048 m: 1 m² = about 10.764 ft², applied at full precision and rounded for display, as in the metric worked example (12 m² = 129.2 ft²).
Are measurements stored?
No. The calculation runs entirely in the browser. Dimensions are never uploaded, stored or tracked.
Related tools
Paint Calculator⌂Estimate paint for a room from its dimensions — wall area minus standard doors and windows, multiplied by coats and divided by the coverage rate.Open tool →Tile Calculator⌂Count tiles for a floor or wall from the area and tile size — including the grout gap in each tile's effective area, a layout waste factor and boxes.Open tool →Flooring Calculator⌂Work out how many boxes of laminate, vinyl or engineered flooring a room needs — area plus the waste factor for the laying pattern, divided by box coverage.Open tool →Mulch Calculator⌂Calculate mulch volume from bed area and depth in cubic yards, cubic feet and standard bags — with a depth-to-coverage table for one cubic yard.Open tool →Gravel Calculator⌂Calculate gravel volume and weight for paths, drives and drainage — volume from area and depth, weight from the stated density of the material chosen.Open tool →BTU Calculator⌂Estimate the BTU size for heating or cooling a room from floor area with published rule-of-thumb adjustments for ceiling height, insulation, sun and occupants.Open tool →
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