How this calculator works
- Step 1Shapepick oneSplit odd shapes into simple ones.
- Step 2Measureone unitUse the same unit for every side.
- Step 3Areaunit²Shown in your unit, m², ft² and gaj.
Area is the space a flat shape covers, counted in squares of your unit. Each shape has its own formula; the calculator applies it and converts the answer.
Worked example: a 30 × 40 ft plot
- Rectangle
length × width
- Area30 ft × 40 ft1,200 ft²
- In square metres1,200 × 0.3048²111.48 m²
- In gaj1,200 ÷ 9133.33 gaj
A larger 40 × 60 ft plot is 2,400 ft², or 266.67 gaj.
Other shapes
- Triangle30 m²Base 10 m, height 6 m: half of base × height.
- Trapezoid32 ft²Sides 10 and 6 ft, 4 ft apart: average side × height.
- Circle153.94 m²Radius 7 m: π × r².
Height always means the distance at right angles to the base, not a slanted side.
Assumptions and limits
- Flat shapesSlopes and curves in the ground are ignored.
- Exact units1 ft = 0.3048 m; 1 gaj = 9 ft².
- Ellipse perimeterRamanujan’s close approximation.
- Regional unitsBigha and kanal are in the Land Area Converter.
From area to materials
Area is the starting point for most home estimates: tiles, paint and land.
For floors and walls, the tile calculator adds grout and waste, and the paint calculator works out litres. To convert Indian land units such as bigha or guntha, use the land area converter.
Common mistakes
Mistake: Using a slanted side as the height.
Instead: Measure straight across at a right angle.
Mistake: Mixing feet and inches.
Instead: Convert to one unit first: 10 ft 6 in = 10.5 ft.
Mistake: Using the diameter as the radius.
Instead: The radius is half the diameter.
Checking the method
A separate script re-works every golden value with the shoelace formula and numerical integration, without the area formulas.
Read how we test our calculators, or browse more maths calculators.