The calculation, without hidden assumptions
Circle measurements are all tied to one radius, but users rarely start with the same quantity. This calculator accepts radius, diameter, circumference or area as the known value and solves back to radius first, so the relationships stay consistent across every output.
How to use this calculator
Choose the circle value you already know.
Enter that positive measurement.
Read radius, diameter, circumference and area together, with the inverse relationship used to recover radius.
Where people use it
- •Round-table and pipe geometry
- •Layout and fabrication checks
- •Math and drafting work
Example: radius 5
A radius of 5 gives diameter 10, circumference about 31.416 and area about 78.540 square units.
What the result does not assume
- •Length outputs use the same unit as the input length; area is in the corresponding square unit.
- •If you start from area, the entered unit must already be a square unit and the recovered radius uses its matching linear unit.
Frequently asked questions
What is the difference between radius and diameter?+
The radius runs from center to edge; the diameter crosses the circle through the center and is twice the radius.
How is circumference calculated?+
Circumference is 2πr, equivalent to π times the diameter.
Can I start with area?+
Yes. The calculator recovers radius using √(area/π) and then calculates the remaining values.
Semantic next steps
Continue the calculation
These links move to a different input, formula or project stage rather than a keyword variation of this page.
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Give readers the live calculator without rebuilding the math. Copy the responsive embed in one click, or customize width, height, border and corner radius before publishing. The branded MAXScanner attribution stays visible.
Keep the result connected to the real job
MAXScanner keeps the formula and assumptions beside the result so you can verify the number before using it in a drawing, estimate, specification, worksheet or document. Where a supplier, manufacturer, drawing or applicable standard owns a requirement, that source remains authoritative.