ToolwebHow to use this tool
- Choose a shape to reveal the dimensions it needs.
- Enter every dimension in the same unit and choose its display label.
- Compare area, perimeter and diagonal, or volume and surface area.
A 3–4–5 right triangle
- Input and settings
- Right triangle; perpendicular legs 3 cm and 4 cm
- Result
- Area 6 cm²; hypotenuse 5 cm; perimeter 12 cm
The inputs are perpendicular legs, not any arbitrary pair of sides.
Keep dimensional units consistent
Lengths in centimeters produce areas in square centimeters and volumes in cubic centimeters. Selecting a unit label does not convert the numeric inputs. If your measurements mix meters and centimeters, normalize them with the unit converter first.
Circle and sphere inputs are radii, not diameters. Cylinder surface area includes the curved side and both circular ends. An open container, or material with thickness, may require a different physical surface calculation.
Understand what the diagram represents
The diagram is a visual aid for understanding the dimensions. Extremely long or flat shapes are constrained to remain visible on screen; it is not a printable, full-scale cutting template.
Dimensions must be finite numbers from 0.000001 to one billion. Results involving π or square roots use browser numeric arithmetic and display up to 12 significant digits. Review tolerances separately for precision design.
Common questions
Can I calculate an arbitrary triangle?
The triangle mode is specifically for right triangles. Its two inputs must be the perpendicular legs for the hypotenuse and perimeter to be valid.
Does changing the unit label change the numbers?
No. It changes the dimensional label on the same numeric inputs. Use the unit converter to convert the numbers themselves.