Circle Calculator
Compute circle area and circumference from the radius — geometry homework solved. Enter r=5 and read both measures at once — free, local, no signup.
How to Use the Circle Calculator
Similar Tools You Might Need
See allProbability Calculator
Compute simple probability as favorable outcomes divided by total outcomes — coin flips, dice rolls, card draws. See 3 in 10 read as 30.0% instantly — free, local, no signup.
Rectangle Area Calculator
Compute rectangle area and perimeter from length and width — flooring, paint, fencing estimates. A 12×15 ft room needs 180 sq ft of flooring — free, runs locally.
Geometry Calculator
Solve geometry essentials — areas, perimeters, volumes, angles — with diagrams described. Cover homework shapes in one tab — free, local, no signup.
ROI Calculator
Measures return on investment by comparing net gain or loss against the original cost, expressed as both a percentage and a dollar amount. Essential for marketing campaign evaluation, equipment purchase decisions, real estate investment analysis, and comparing investment opportunities.
Body Surface Area Calculator
Compute body surface area with four formulas (Mosteller, Du Bois, Haycock, Gehan & George) for medication dosing and physiology. Get m² from height and weight — free, local, informational only.
Frequently Asked Questions
Area from diameter?
Halve it yourself first, then enter the radius: d=10 means r=5, area ≈ 78.5. The tool accepts radius only.
Circumference too?
Always alongside area — one radius entry shows both to one decimal.
Exact π forms?
No — decimals only (25π shows as 78.5). Copy π-exact forms for homework by hand.
Do circle measures upload?
No — math runs locally in your browser. Numbers never leave your device.
Related Calculator Tools
Geometry Calculator
Solve geometry essentials — areas, perimeters, volumes, angles — with diagrams described. Cover homework shapes in one tab — free, local, no signup.
Triangle Area Calculator
Calculate triangle area three ways — base and height, three sides (Heron), or two sides plus included angle. Pick the method matching your knowns. Numbers never leave your device — every calculation runs locally in your browser.
Last updated October 2026