Area of a Circle Calculator

Created by Łucja Zaborowska, MD, PhD candidate
Reviewed by Dominik Czernia, PhD and Jack Bowater
Last updated: Nov 21, 2022

The area of a circle calculator helps you compute the surface of a circle given a diameter or radius. Our tool works both ways - no matter if you're looking for an area to radius calculator or a radius to the area one, you've found the right place

We'll give you a tour of the most essential pieces of information regarding the area of a circle, its diameter, and its radius. We'll learn how to find the area of a circle, talk about the area of a circle formula, and discuss the other branches of mathematics that use the very same equation.

How to calculate the area of a circle? Area of a circle formula

So, let's see how to find the area of a circle. There are several ways to achieve it. Here, we can calculate the area of a circle using a diameter or using a radius.

💡 The diameter is the line that crosses the center of the figure and touches both of its margins. The radius begins at the center of the figure and ends at the figure's margin.

You can find the diameter of a circle by multiplying the radius of a circle by two:

Diameter = 2 × Radius.

Area of a circle radius. The radius of a circle calculator uses the following area of a circle formula:

Area of a circle = π × r2.

Area of a circle diameter. The diameter of a circle calculator uses the following equation:

Area of a circle = π × (d/2)2,

where:

  • π is approximately equal to 3.14. It doesn't matter whether you want to find the area of a circle using diameter or radius - you'll need to use this constant in almost every case.

🔎 Another relevant aspect of circles is their circumference. You can learn more about it and its relationship with area in our circle formula calculator.

Now that you know how to calculate the area of a circle, we encourage you to discover similar topics:

  • Circle circumference and perimeter.
  • Sector of a circle.
  • Pie chart.
  • Area of the largest circle in a square.
Image of the sector of the circle and radius.
  • A sector of a circle is a section of a circle between two radii. You can think of it as a giant slice of pizza.
  • If you want to know how to draw a circle?, the equation for the coordinates and the center of a circle in the coordinate system might come in handy.

Also, why don't you try our other circle calculators:

Image of the segment of the circle.

It's a "cut-off" part of a circle, limited by a chord or a secant.

Image of the circle angle.

It's an angle with the vertex in the center, whose arms extend to the circumference.

How to use the area of a circle calculator? Diameter to area and radius to area.

Image of the special lines of the circle - diameter, radius, chord, and circumference.

You can easily calculate everything, the area of a circle, its diameter, and its radius, using our area of a circle calculator in a blink of an eye:

  1. Determine whether your given value is a diameter or a radius using the picture on the right and definitions available in the section above (you can calculate the area of a circle using its diameter as well as radius).

  2. Enter your value into the proper field of the calculator.

  3. It didn't take long - your results are here! We decided to include the step-by-step solution and all the most important data right below the calculator.

That is how to calculate the area of a circle in no time 😉.

🔎 The area is not the only property related to the diameter, as the circumference is too. Learn more about it in our circumference to diameter calculator.

Why do we need the surface area of a circle calculators?

The circle's area found with both the radius and diameter calculators serves as a base for many other equations - not only in mathematics but also in everyday life! Here are a few examples where knowing how to find the area of a circle might be useful:

  • We need to know the surface area of a circle in order to calculate a cone's volume and its surface area 🎉.

  • Your pizza party wouldn't be complete without estimating the pizza's size based on the diameter to area calculator 🍕.

  • We use calculations similar to this one when obtaining information about a sphere, such as a sphere volume 🌐.

  • Do you fancy nice dresses? Maybe you love to sew? Discover Omni's circle skirt calculator! Efficient sewing has never been easier 👗.

Łucja Zaborowska, MD, PhD candidate
circle with radius marked
Radius (r)
in
Diameter (d)
in
Area (A)
in²
Check out 8 similar circle calculators ⭕
Arc lengthCircle calc: find c, d, a, rCircumference… 5 more
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