Geometry

# Area of a circle calculator

Area of a circle calculator - calculating area of a circle online. Area of a circle - is a numerical characteristic that characterizes the size of a plane bounded by a circle line. Area of a circle can be calculated using the number pi and the radius of the circle, or using other known input data. Our calculator will help you to calculate the area of a circle for free online or to check the already performed calculations.

Table with circle area formulas (at the end of the page)

1

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2

## Circle area through diameter

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D - diameter

3

## Area of a circle along the circumference

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- circumference

4

## Area of a circle through a square inscribed in a circle

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a - side

5

## Area of the circle inscribed in a square

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A - side

6

## Area of the circle described around an arbitrary triangle

This formula is applicable only if a circle can be described around a triangle, that is, all three vertices of the triangle must lie on the line of the circle. The triangle in this case can be any.

To calculate the area of a circle, first calculate the semi-perimeter of a triangle

... preparation ...

a - side
b - side
c - side

7

## Area of a circle described near an equilateral triangle

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a - side

8

## Area of a circle described around an equilateral triangle, calculated from the height of the triangle

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h - height

9

## Area of a circle about an isosceles triangle

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a - side
b - base

10

## Area of the circle described about a right triangle

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a - side
b - side

11

## Area of a circle inscribed in an isosceles triangle

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a - side
b - base

12

## Area of a circle inscribed in an isosceles triangle, calculated on the sides of the triangle and the angle between them

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b - side
α - angle between parties

13

## Area of a circle inscribed in a right triangle

... preparation ...
a - side
b - side
c - side

14

## Area of a circle inscribed in a right triangle, calculated by the side and angle

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b - side
α - angle at base

15

## Area of a circle inscribed in an equilateral triangle

... preparation ...
a - side

16

## Area of a circle inscribed in an isosceles trapezium, calculated from the base of the trapezium and the angle at the base

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b - side
α - angle at base

17

## Area of a circle described near an isosceles trapezium, calculated along the sides of the trapezium, its diagonal and base

To calculate the area of a circle, first calculate the semi-perimeter of a triangle ABC

... preparation ...

a - side
c - side
d - diagonal

18

## Area of the circle described near the rectangle

... preparation ...
a - side
b - side

19

## Area of a circle described near a regular polygon

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a - side
N - the number of sides of the polygon

20

## Area of a circle described about a regular hexagon

... preparation ...
a - side

Note:

If the angle is specified in radians in the source data, then for conversion to degrees you can use the formula: 1 radian × (180/π)° = 57,296°

## Table with circle area formulas

 initial data(active link to go to the calculator) sketch formula 1 radius 2 diameter 3 circumference 4 side of a square 5 side of a square 6 side of the triangle where 7 side of an equilateral triangle 8 equilateral triangle height 9 side and base 10 side at right angle of triangle 11 side and base 12 sides and angle between them 13 side of a right triangle 14 side and angle at the base of the triangle 15 side of an equilateral triangle 16 side and angle at the base of the trapezoid 17 sides and diagonal of the trapezoid where 18 side of the rectangle 19 side and number of sides of the polygon 20 hexagon side