Area Calculator
Compute the area of a rectangle, circle or triangle.
Inputs
- Shape
- Length / Base / Radius (m)
- Width / Height (m)
What it does
Area of a rectangle, circle or triangle.
Where it's used
Flooring, painting, plot sizes and cross-sections.
How to use it
- Choose the shape.
- Enter the dimensions — for a circle use the radius, for a triangle the base and perpendicular height.
- Read the area.
The formula explained
- Rectangle
- length × width
- Circle
- π × r²
- Triangle
- ½ × base × height
Worked example
A circular area with a 2.5 m radius.
Inputs:
- Shape: Circle
- Length / Base / Radius: 2.5 m
The calculator gives:
- Result: 19.635 m²
Tips and common mistakes
- Split irregular areas into rectangles and triangles and add them.
- A triangle needs the height at right angles to the base, not the sloping side.
- Order 5–10 % extra material for cuts and waste.
Questions people ask
How do I convert between area units?
1 m² ≈ 10.76 sq ft, 1 hectare = 10 000 m² and 1 acre ≈ 4 047 m². Area units go with the square of length units, so 1 m² = 10 000 cm², not 100.
What if I know the diameter of a circle?
Use A = π × d² / 4, or halve the diameter to get the radius first. A 5 m diameter circle has the same 19.6 m² as the 2.5 m radius example.
How do I find the area of a triangle from its three sides?
Heron’s formula: s = (a + b + c) / 2, then A = √(s(s − a)(s − b)(s − c)). A 3-4-5 triangle has s = 6 and an area of 6 m².
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Enter your values to get the result with the formula, substituted values and an explanation of each step.