Area Calculator
Calculate the area of a circle, rectangle, square, or triangle — pick a shape and enter its dimensions.
- Free to use
- Accurate results
- No registration required
- Works on all devices
Choose a shape and enter its dimensions to calculate its area.
Your result
78.54
Area
ShapeCircle
AI explanation
Formula
Circle: π × radius²; Rectangle: length × width; Square: side²; Triangle: base × height ÷ 2Worked example
Circle with radius 5
| Field | Value |
|---|---|
| Shape | circle |
| Radius | 5 |
| Area | 78.539816 |
| Shape | Circle |
Assumptions
- Triangle area uses the base × height ÷ 2 formula, which needs the perpendicular height to the chosen base — for a triangle where you only know all three side lengths, use the Triangle Calculator instead (it uses Heron's formula).
Frequently asked questions
Why do the input fields change when I pick a different shape?
Each shape needs different measurements — a circle needs only a radius, while a rectangle needs both a length and a width — so the form shows only the fields relevant to your chosen shape.
I need perimeter or other properties too — is there a more detailed calculator?
Yes — see the dedicated Circle Calculator, Rectangle Calculator, Square Area Calculator, or Triangle Calculator for perimeter, diagonal, and other properties specific to that shape.
Can I calculate the area of a triangle from its three side lengths instead?
Use the Triangle Calculator for that — it computes area from three side lengths using Heron's formula, rather than base and height.