Every flat shape has its own area formula, and most come down to a length times a height. A trapezoid with parallel sides of 10 m and 6 m, 4 m apart, has an area of (10 + 6) ÷ 2 × 4 = 32 m², or 344.4 ft². Pick one of ten shapes, type its measurements in any unit and the calculator gives the area with the formula and the numbers put in, plus hectares and acres for large plots.
Area formulas for ten shapes
| Shape | Formula | Measure |
|---|---|---|
| Rectangle or square | length × width | the two sides |
| Triangle | base × height ÷ 2 | height at right angles to the base |
| Trapezoid | (a + b) ÷ 2 × height | the two parallel sides |
| Parallelogram | base × height | not the slanted side |
| Rhombus or kite | d₁ × d₂ ÷ 2 | the two diagonals |
| Circle | π × r² | the radius (half the diameter) |
| Ellipse | π × a × b | half the long and half the short axis |
| Sector (slice) | π × r² × angle ÷ 360 | radius and angle in degrees |
| Ring (annulus) | π × (R² − r²) | outer and inner radius |
| Regular polygon | sides × side × apothem ÷ 2 | number of sides and one side |
Regular polygons with a side of 1
The area of a regular polygon grows with the square of its side, so this table works for any size: multiply by the side squared.
| Sides | Name | Area for side 1 |
|---|---|---|
| 3 | Equilateral triangle | 0.4330 |
| 4 | Square | 1 |
| 5 | Pentagon | 1.7205 |
| 6 | Hexagon | 2.5981 |
| 8 | Octagon | 4.8284 |
| 10 | Decagon | 7.6942 |
| 12 | Dodecagon | 11.1962 |
A hexagonal paver with 20 cm sides covers 2.5981 × 0.2² = 0.104 m², so you need about 9.6 of them per square meter, before cuts.
Measuring the real thing
The height of a triangle, a trapezoid or a parallelogram is always the straight distance at right angles to the base, not the length of a slanted side. For an oval table or flower bed, measure the longest and the shortest width and halve them for a and b. A pizza slice is a sector: a 30 cm pizza cut into 8 has slices of π × 15² × 45 ÷ 360 = 88.4 cm².
The calculator works without a connection once zet4u is saved on your phone (how offline works), so you can measure a garden or a room where there is no signal.
Frequently asked questions
How do I find the area of a trapezoid?
Average the two parallel sides and multiply by the height: (a + b) ÷ 2 × h. With bases of 10 and 6 m and a height of 4 m, the area is 8 × 4 = 32 m².
What is the area of a rhombus or a kite?
Half the product of the diagonals: d₁ × d₂ ÷ 2. A kite with diagonals of 6 and 4 cm has an area of 12 cm².
How do I find the area of an irregular room or plot?
Split it into rectangles and triangles, find each area with the calculator and add them up. For an L-shaped room, two rectangles are enough.
What is the area of a regular hexagon?
About 2.598 × side². A hexagon with 10 cm sides covers 259.8 cm². The calculator handles any regular polygon from 3 sides up.
How many square feet are in a square meter?
10.7639. One square foot is exactly 0.09290304 m², because a foot is exactly 0.3048 m.
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