Circle Area Calculator
Enter a circle radius to calculate the exact area in terms of π and a decimal approximation, with the formula A = πr² shown step by step.
Circle area calculator using radius squared times pi
Use this circle area calculator when a problem gives the radius and asks for π times the radius squared.
The result keeps π in the exact form first, then shows a decimal approximation in square units.
Examples include decimal radii such as 4.89 and 7.6, where rounding too early can noticeably change the area.
Features
- Direct radius input for whole numbers and decimals.
- Exact result written as a multiple of π.
- Decimal area approximation in square units.
- Visible radius-squared and multiplication steps.
- Quick examples for common πr² calculations.
Example expressions
r = 4.89r = 7.6r = 1.4
Example problems with answers
r = 4.89- The exact area is 23.9121π, approximately 75.122956 square units.
r = 7.6- The exact area is 57.76π, approximately 181.458392 square units.
Related formulas
Circle area: A = πr².If the diameter is d, then r = d/2.Area units are squared, such as cm² or m².
FAQ
What is the formula for the area of a circle?
The formula is A = πr², where r is the circle radius.
Can I enter a decimal radius?
Yes. Enter the complete decimal value and the calculator will square it before multiplying by pi.
What if I only know the diameter?
Divide the diameter by 2 to get the radius, then enter that radius.
Why is the result written with pi and as a decimal?
The π form is exact, while the decimal is an approximation that is convenient for measurements.
What units should I use for the answer?
Use the square of the radius unit. A radius in centimeters produces an area in square centimeters.
Sources and review
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