How do you find rectangle area?
Multiply length by width.
Area Calculator
One place for everyday plane-area formulas with a shape selector.
Select a shape
Choose a shape and enter the required dimensions.
About this calculator
How to use Area Calculator, plus the formulas and logic behind the results.
Tool description
Area measures the size of a 2D region. Each common shape has a simple closed-form formula.
How to use
- Select the shape.
- Enter positive dimensions as prompted.
- Select Calculate.
- Read the area result.
Formulas & reference
Rectangle: L × WTriangle: (1/2) × base × heightCircle: π r²Trapezoid: (1/2)(a + b) h
Area reminders
- Keep units consistent
- Triangle height is perpendicular
- Trapezoid bases are the parallel sides
- Circle needs only radius
Calculation logic
Dispatches to the selected formula. Circle uses M_PI.
All lengths must be positive.
Area Calculator FAQ
Common questions about this calculator and how to use the results.
How do you find triangle area?
Half of base times height.
How do you find circle area?
π times radius squared.
How do you find trapezoid area?
Average the parallel bases and multiply by height.
Can dimensions be zero?
No—enter positive lengths.
Does this do surface area?
No—use the surface area calculator for 3D solids.