Geometry Calculator

Common geometry formulas

• Circle: area = πr², circumference = 2πr.
• Square: area = a², perimeter = 4a.
• Rectangle: area = a × b, perimeter = 2(a + b).
• Triangle: area = ½ × base × height.
• Cylinder: volume = πr²h, surface area = 2πr² + 2πrh.

Enter values in any single unit (for example metres) — results are returned in the matching square (area) or cubic (volume) unit. All calculations run locally in your browser.

Frequently Asked Questions

How do you find the area of a circle?

Area = π × r², and the circumference (perimeter) = 2 × π × r. For a radius of 5, the area is about 78.54 and the circumference about 31.42.

How do you calculate the volume of a cylinder?

Volume = π × r² × h. The lateral surface area = 2 × π × r × h, and the total surface area = 2 × π × r² + 2 × π × r × h.

What is the formula for the area of a triangle?

Area = ½ × base × height. This works for any triangle as long as the height is measured perpendicular to the chosen base.

How do I find the perimeter of a rectangle?

Perimeter = 2 × (length + width), and the area = length × width.