Why Use This Tool?
Area and volume formulas are easy to forget and embarrassing to get wrong mid-project. This calculator covers eight common shapes — circle, rectangle, triangle, square for flat surfaces; sphere, cylinder, cone, cube for volumes — with the fields changing to match the shape you pick.
Each result uses the standard formula with full precision, so a 2-radius circle really is 12.566 square units, not a rounded guess.
How It Works
- Pick a shape from the dropdown — the input fields adjust automatically.
- Enter the shape's measurements.
- Read the area, volume, perimeter or surface area.
Frequently Asked Questions
How do I calculate the area of a circle?
Area = π × r². Enter the radius and the tool applies π at full precision — a radius of 2 gives 12.566, not a rounded 12.57.
How do I calculate the volume of a cylinder?
Volume = π × r² × h. Pick cylinder, enter the radius and height, and the volume plus surface area both appear.
Which shapes include surface area?
The 3D shapes do: sphere (4πr²), cylinder (2πr(r+h)) and cone (πr√(r²+h²)) all show surface area alongside volume.
Tips & Things to Watch
- Keep units consistent — mixing feet and inches in one shape corrupts the result.
- Triangle area needs base and perpendicular height, not the side length.
- Results are unit-cubed for volumes: enter feet, get cubic feet.