Calculadora de Área do Círculo
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
A = π × r²
About this calculator
The Circle Area Calculator is an online tool that quickly calculates the area of a circle from its radius. The formula used is A = π × r², where A is the area and r is the radius. The value of π (pi) is approximated as 3.14159. Simply enter the radius in any unit of measurement and the calculator returns the area in the same unit squared.
This calculator is useful in various practical situations, such as calculating the area of circular plots of land, determining the amount of material needed to cover a round surface, or solving geometry problems in everyday life. For example, when planning a circular garden, you can use the tool to find out how many square meters of grass are needed.
When using the calculator, remember that the radius is the distance from the center to the edge of the circle. If you have the diameter, divide it by two to get the radius. The tool can also be used to convert areas between units, but make sure the radius is in the correct unit for the desired result. Be careful with rounding: for greater precision, use π with more decimal places or the built-in constant of your device.
Frequently asked questions
Can I use the diameter instead of the radius?
No, the calculator only accepts the radius. If you have the diameter, divide it by 2 to get the radius before entering.
What value of π does the calculator use?
The calculator uses π = 3.14159. For more precise calculations, you can use a more exact value manually.
Does the calculator work with any unit of measurement?
Yes, as long as you enter the radius in a consistent unit. The area will be in the same unit squared.
Why does the result seem different from expected?
Check if you entered the radius correctly. Common mistakes include using the diameter instead of the radius or confusing units.
Can I calculate the area of a semicircle?
Yes, calculate the area of the full circle and then divide by 2. The calculator does not have a specific semicircle function.