Area calculator
Calculator
The calculator needs JavaScript. The tables below give the same numbers for common cases.
How it is worked out
- Area = length × width = 8 × 5 = 40.
| Inputs | Answer |
|---|---|
| Shape: Rectangle (a = length, b = width); a: 8; b: 5; c: 3 | The area of the rectangle is 40 square units. |
| Shape: Circle (a = radius); a: 3; b: 1; c: 1 | The area of the circle is 28.274334 square units. |
| Shape: Triangle (a = base, b = height); a: 10; b: 6; c: 1 | The area of the triangle is 30 square units. |
| Shape: Trapezoid (a, b = parallel sides, c = height); a: 8; b: 5; c: 3 | The area of the trapezoid is 19.5 square units. |
How to use it
Area is the amount of flat surface a shape covers, measured in square units. Each shape has its own formula: rectangle length × width, triangle ½ × base × height, circle π × r², trapezoid ½ × (a + b) × height, parallelogram base × height, ellipse π × a × b.
Pick the shape, read what a, b and c mean from its label, and enter your numbers. The steps show the formula with your values. Use the same unit for every side; the answer is in that unit squared.
Frequently asked questions
What is the area of a rectangle 8 by 5?
8 × 5 = 40 square units.
How do I find the area of a circle?
Multiply π by the radius squared. For radius 3: π × 9 ≈ 28.274.
Why is the answer in square units?
Area counts unit squares; metres give square metres, feet give square feet.
Method: standard arithmetic shown step by step; no outside data is used. Checked 2026-11-12.
About · How we verify this · Editorial policy · Corrections
General information only. Results are plain arithmetic on the numbers you enter; check anything important (money, health, school work) against your own records or the official source.