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Circle Diameter Calculator
Diameter of a circle from radius, circumference or area.
ruler Free Online Tool
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Diameter
Compare Your Options And Get Clear Answers
Diameter of a circle from radius, circumference or area.
Circle Diameter Estimator
Enter your numbers below for an instant estimate.
0
💡 Tip: d = 2r = C / pi.
How It Works
Key concepts behind this calculator
1
Enter Values
Fill in each field with your own numbers.
2
Calculate
Results update as you change the inputs.
3
Review
Read the breakdown and the explanation.
4
Adjust
Change values to compare scenarios.
Quick Reference Guide
Circle Quick Guide
Typical values for reference.
| Radius | Diameter | Circumference | Area |
|---|---|---|---|
| 1 | 2 | 6.2832 | 3.1416 |
| 5 | 10 | 31.4159 | 78.5398 |
| 7 | 14 | 43.9823 | 153.938 |
| 10 | 20 | 62.8319 | 314.159 |
| Rule of Thumb | Check inputs | Use as a guide | Round sensibly |
Common Questions
Circle Diameter Calculator FAQ
Answers to common questions about this calculator.
Divide by pi.
2 x sqrt(area / pi).
d = 2r = C / pi.
It is an estimate based on the inputs you enter. Check real quotes, labels or official guidance for important decisions.