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Geometry workspace
Change a measurement and see how the shape and answer change. Solve a missing dimension, then save a scenario to compare later.
Your scenarios
Saved on this device. Select a scenario to restore its measurements and units.
Worked example: a 3 × 4 rectangle
With length 3 m and width 4 m, area is 12 m², perimeter is 14 m and diagonal is 5 m. If you know area 12 m² and width 4 m, choose the missing-length mode: 12 ÷ 4 = 3 m.
Common questions
Can I enter different units?
Yes. Choose a unit beside each measurement. Inputs are converted to a common unit before calculation; output menus change how results are shown.
How do I compare alternatives?
Save one scenario, change the measurements and save another. The scenario buttons show the main result. Select a saved scenario to restore its inputs and full diagram.
Is this a construction safety check?
No. These calculations describe ideal geometry. They do not determine structural suitability or a safe construction tolerance.
Dedicated hypotenuse calculator · Area calculator · Connected projects
Report a calculation issue. Please describe the units and expected method; omit private measurements.
Methods and limits
Rectangle: area = length × width, perimeter = 2 × (length + width), diagonal = √(length² + width²). A missing side = area ÷ known side.
Right triangle: hypotenuse² = leg A² + leg B². A missing leg = √(hypotenuse² − known leg²). Circle: area = πr², circumference = 2πr. Inverse modes rearrange these equations.
Measurements must be positive. A right triangle's hypotenuse must exceed each known leg. These are geometric quantities, not construction or safety recommendations. Finite entered components are limited to 10¹² and canonical/results to 10¹⁵; extremely small or large calculations may exceed numerical limits. Units use the shared reviewed registry; floating point values are rounded for display.
Methods are elementary mathematical derivations checked by independent numerical and algebraic tests. Unit definitions use the existing NIST conversion reference.