⭕ Circle Calculator
Calculate all circle measurements
Distance from center to edge
Circle Formulas
Radius (r)
Diameter (d)
Circumference (C)
Area (A)
Quick Reference
What is Pi (π)?
π ≈ 3.14159265358979...
An irrational number that never ends or repeats
Pi (π) is the ratio of a circle's circumference to its diameter. This ratio is constant for all circles, regardless of size.
Why is π important?
- Appears in all circle calculations
- Used in trigonometry, physics, and engineering
- One of the most important constants in mathematics
- Celebrated on Pi Day (March 14 = 3/14)
Common Approximations
Real-World Applications
🏗️ Construction
- • Calculate circular pool dimensions
- • Design round patios and decks
- • Determine circular driveway size
- • Plan circular garden beds
🍕 Everyday Use
- • Pizza size comparisons
- • Circular table seating
- • Wheel and tire measurements
- • Round cake/pie servings
🔧 Engineering
- • Gear and pulley design
- • Pipe diameter calculations
- • Circular motion physics
- • Wheel circumference for distance
🎨 Design
- • Logo and graphic design
- • Circular patterns and mandalas
- • Round window dimensions
- • Circular art layouts
Circle Parts
How to Use This Calculator
1Enter Your Values
Input the required values in the calculator fields above. Make sure all inputs are valid numbers.
2Click Calculate
Press the "Calculate" button to perform the calculation and see your results.
3Review Results
Review the calculated results displayed below. Use these values for your needs.
About Circle Calculator
The Circle Calculator is a useful tool for calculating circle values. This calculator helps you quickly and accurately determine the results you need for your calculations.
When to Use This Calculator
- Quick Calculations: Get instant results without manual computation
- Accuracy: Ensure precise calculations every time
- Planning: Use for project planning and estimation
- Verification: Double-check your manual calculations
Why Use Our Calculator?
- ✅ Instant Results: Get accurate calculations immediately
- ✅ Easy to Use: Simple interface for all skill levels
- ✅ 100% Free: No registration or payment required
- ✅ Mobile Friendly: Works on all devices
- ✅ Accurate: Precise mathematical calculations
Tips for Best Results
- Double-Check Inputs: Verify all values before calculating
- Use Valid Numbers: Ensure inputs are valid numbers
- Review Results: Check results for reasonableness
- Clear and Retry: Clear inputs if you need to recalculate
Frequently Asked Questions
How to Use This Calculator
Enter Your Values
Input the required values in the calculator fields above. Make sure all inputs are valid numbers.
Click Calculate
Press the "Calculate" button to perform the calculation and see your results.
Review Results
Review the calculated results displayed below. Use these values for your needs.
About Circle Calculator
The Circle Calculator is a useful tool for calculating circle values. This calculator helps you quickly and accurately determine the results you need for your calculations.
When to Use This Calculator
- Quick Calculations: Get instant results without manual computation
- Accuracy: Ensure precise calculations every time
- Planning: Use for project planning and estimation
- Verification: Double-check your manual calculations
Why Use Our Calculator?
- ✅ Instant Results: Get accurate calculations immediately
- ✅ Easy to Use: Simple interface for all skill levels
- ✅ 100% Free: No registration or payment required
- ✅ Mobile Friendly: Works on all devices
- ✅ Accurate: Precise mathematical calculations
Tips for Best Results
- Double-Check Inputs: Verify all values before calculating
- Use Valid Numbers: Ensure inputs are valid numbers
- Review Results: Check results for reasonableness
- Clear and Retry: Clear inputs if you need to recalculate
How do I measure the radius of a circle?
Find the center point and measure to any point on the edge. If you can only measure diameter (across), divide by 2 to get radius.
What if I only know the area?
Use r = √(A / π) to find radius. For example, if area = 78.54, then r = √(78.54 / 3.14159) = √25 = 5.
Why is the area formula πr² and not 2πr?
2πr gives circumference (1D perimeter). πr² gives area (2D space inside). The squared term accounts for two dimensions.
How accurate should I make my calculations?
For everyday use, π = 3.14 is fine. For construction, use 3.14159. For engineering/science, use your calculator's π button (many more digits).
Can I calculate part of a circle?
Yes! For a sector (pie slice): multiply circle area by (angle/360°). For arc length: multiply circumference by (angle/360°).