Area Calculator
Compute 2-D surface area for the four most common plane shapes. Pick rectangle, triangle, circle or trapezoid, enter the dimensions, and get the area plus perimeter/circumference where defined, with every formula fully substituted.
TheCalculators — Area Calculator
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Area
40 units²
rectangle · A = length × width
- Shape
- rectangle
- Inputs
- length = 8, width = 5
- Formula
- A = length × width
- Area
- 40 units²
- Perimeter
- 26 units
Step-by-step
- 1Write the formulaA = length × width
- 2Substitute valuesA = 8 × 5 = 40
- 3ResultA = 40 units²
Area formulas reference
Most useful next
Formula
Rectangle: l·w · Triangle: ½bh · Circle: πr² · Trapezoid: ½(a+b)h
Pro tips
- • A trapezoid is the average of its two parallel sides times the height — that is exactly what ½(a+b)·h computes.
- • All results are in square units; if lengths are metres the area is square metres (m²).
- • For a triangle with three known sides but no height, use Heron’s formula in the Triangle Calculator.
FAQ
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