Area of a Circle Calculator

Circle Calculator

Inputs:

Radius:		or
Diameter		or
Circumference:
Unit:

Result:

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The area of a circle with diameter 10 is 78.54

Formulae:

A = πr² = π(d2)²

A = C²4π

π = 3.1415
A = area
C = circumference or perimeter
r = radius, d = diameter

Solution Steps:

Area of a circle in terms of radius:

Area = π·r² = 3.14·5² = 78.54 square mm^(*)

Area of a circle in terms of diameter:

Area = π·(d2)² = 3.14·(102)² = 3.14·(5)² = 78.54 square mm^(*)

Area of a circle in terms of circumference:

Area = C²4π = 31.42²4π = 987.22(4·3.14) = 987.2212.56 = 78.54 square mm^(*)

^(*) 78.539816339745 mm, exactly or limited to the precision of this calculator (13 decimal places).

Note: for simplicity, the operations above were rounded to 2 decimal places and π was rounded to 3.14.

Result in other units of area:

A circle of radius = 5 or diameter = 10 or circumference = 31.42 mm has an area of:

7.854 × 10^-11 square kilometers (km²)
7.854E-5 square meters (m²)
0.7854 square centimeters (cm²)
78.54 square millimeters (mm²)
3.03245 × 10^-11 square miles (mi²)
9.39331E-5 square yards (yd²)
0.000845398 square feet (ft²)
0.121737 square inches (in²)

Use the this circle area calculator below to find the area of a circle given its diameter, or other parameters. To calculate the area, you just need to enter a positive numeric value in one of the 3 fields of the calculator. You can also see at the bottom of the calculator, the step-by-step solution.

Formula for area of a circle

Here a three ways to find the area of a circle (formulas):

Circle area formula in terms of radius

A = πr²

Circle area formula in terms of diameter

A = π(d2)²

Circle area formula in terms of circumference

A = C²4π

See below some definitions related to the formulas:

Circumference

Circumference is the linear distance around the circle edge.

Radius

The radius of a circle is any of the line segments from its center to its perimeter. The radius is half the diameter or r = d2.

Diameter

The diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. The diameter is twice the radius or d = 2·r.

The Greek letter π

π represents the number Pi which is defined as the ratio of the circumference of a circle to its diameter or π = Cd . For simplicity, you can use Pi = 3.14 or Pi = 3.1415. Pi is an irrational number. The first 100 digits of Pi are: 3.1415926535 8979323846 2643383279 5028841971 6939937510 5820974944 5923078164 0628620899 8628034825 3421170679 ...

Note:

If you input the radius in centimeters, you will get the answer in square centimeters (cm²), if in inches, will get the answer in square inches (in²) and so on ...

Circumference is often misspelled as circunference.

Relation between radius, diameter, area and circumference of a circle

Note: All values are rounded to two decimal places.

Radius	Diameter	Area	Circumference
0.1	0.2	0.03	0.63
0.15	0.3	0.07	0.94
0.2	0.4	0.13	1.26
0.25	0.5	0.2	1.57
0.3	0.6	0.28	1.88
0.35	0.7	0.38	2.2
0.4	0.8	0.5	2.51
0.45	0.9	0.64	2.83
0.5	1	0.79	3.14
0.55	1.1	0.95	3.46
0.6	1.2	1.13	3.77
0.65	1.3	1.33	4.08
0.7	1.4	1.54	4.4
0.75	1.5	1.77	4.71
0.8	1.6	2.01	5.03
0.85	1.7	2.27	5.34
0.9	1.8	2.54	5.65
0.95	1.9	2.83	5.97
1	2	3.14	6.28
1.01	2.02	3.2	6.35
1.02	2.04	3.27	6.41
1.03	2.06	3.33	6.47
1.04	2.08	3.4	6.53
1.05	2.1	3.46	6.6
1.06	2.12	3.53	6.66
1.07	2.14	3.59	6.72
1.08	2.16	3.66	6.79
1.09	2.18	3.73	6.85
1.1	2.2	3.8	6.91
1.10	2.2	3.8	6.91
1.11	2.22	3.87	6.97
1.12	2.24	3.94	7.04
1.13	2.26	4.01	7.1
1.14	2.28	4.08	7.16
1.15	2.3	4.15	7.23
1.16	2.32	4.23	7.29
1.17	2.34	4.3	7.35
1.18	2.36	4.37	7.41
1.19	2.38	4.45	7.48
1.2	2.4	4.52	7.54
1.20	2.4	4.52	7.54
1.21	2.42	4.6	7.6
1.22	2.44	4.67	7.67
1.23	2.46	4.75	7.73
1.24	2.48	4.83	7.79
1.25	2.5	4.91	7.85
1.26	2.52	4.99	7.92
1.27	2.54	5.06	7.98
1.28	2.56	5.14	8.04
1.29	2.58	5.23	8.11
1.3	2.6	5.31	8.17
1.30	2.6	5.31	8.17
1.31	2.62	5.39	8.23
1.32	2.64	5.47	8.29
1.33	2.66	5.55	8.36
1.34	2.68	5.64	8.42
1.35	2.7	5.72	8.48
1.36	2.72	5.81	8.54
1.37	2.74	5.89	8.61
1.38	2.76	5.98	8.67
1.39	2.78	6.07	8.73
1.4	2.8	6.15	8.8
1.40	2.8	6.15	8.8
1.41	2.82	6.24	8.86
1.42	2.84	6.33	8.92
1.43	2.86	6.42	8.98
1.44	2.88	6.51	9.05
1.45	2.9	6.6	9.11
1.46	2.92	6.69	9.17
1.47	2.94	6.79	9.24
1.48	2.96	6.88	9.3
1.49	2.98	6.97	9.36
1.5	3	7.07	9.42
1.50	3	7.07	9.42
1.51	3.02	7.16	9.49
1.52	3.04	7.25	9.55
1.53	3.06	7.35	9.61
1.54	3.08	7.45	9.68
1.55	3.1	7.54	9.74
1.56	3.12	7.64	9.8
1.57	3.14	7.74	9.86
1.58	3.16	7.84	9.93
1.59	3.18	7.94	9.99
1.6	3.2	8.04	10.05
1.60	3.2	8.04	10.05
1.61	3.22	8.14	10.12
1.62	3.24	8.24	10.18
1.63	3.26	8.34	10.24
1.64	3.28	8.45	10.3
1.65	3.3	8.55	10.37
1.66	3.32	8.65	10.43
1.67	3.34	8.76	10.49
1.68	3.36	8.86	10.56
1.69	3.38	8.97	10.62
1.7	3.4	9.07	10.68
1.70	3.4	9.07	10.68
1.71	3.42	9.18	10.74
1.72	3.44	9.29	10.81
1.73	3.46	9.4	10.87
1.74	3.48	9.51	10.93
1.75	3.5	9.62	11
1.76	3.52	9.73	11.06
1.77	3.54	9.84	11.12
1.78	3.56	9.95	11.18
1.79	3.58	10.06	11.25
1.8	3.6	10.17	11.31
1.80	3.6	10.17	11.31
1.81	3.62	10.29	11.37
1.82	3.64	10.4	11.44
1.83	3.66	10.52	11.5
1.84	3.68	10.63	11.56
1.85	3.7	10.75	11.62
1.86	3.72	10.86	11.69
1.87	3.74	10.98	11.75
1.88	3.76	11.1	11.81
1.89	3.78	11.22	11.87
1.9	3.8	11.34	11.94
1.90	3.8	11.34	11.94
1.91	3.82	11.46	12
1.92	3.84	11.58	12.06
1.93	3.86	11.7	12.13
1.94	3.88	11.82	12.19
1.95	3.9	11.94	12.25
1.96	3.92	12.06	12.31

Radius	Diameter	Area	Circumference
1.97	3.94	12.19	12.38
1.98	3.96	12.31	12.44
1.99	3.98	12.43	12.5
2	4	12.56	12.57
2.00	4	12.56	12.57
2.01	4.02	12.69	12.63
2.02	4.04	12.81	12.69
2.03	4.06	12.94	12.75
2.04	4.08	13.07	12.82
2.05	4.1	13.2	12.88
2.06	4.12	13.32	12.94
2.07	4.14	13.45	13.01
2.08	4.16	13.58	13.07
2.09	4.18	13.72	13.13
2.1	4.2	13.85	13.19
2.10	4.2	13.85	13.19
2.11	4.22	13.98	13.26
2.12	4.24	14.11	13.32
2.13	4.26	14.25	13.38
2.14	4.28	14.38	13.45
2.15	4.3	14.51	13.51
2.16	4.32	14.65	13.57
2.17	4.34	14.79	13.63
2.18	4.36	14.92	13.7
2.19	4.38	15.06	13.76
2.2	4.4	15.2	13.82
2.20	4.4	15.2	13.82
2.21	4.42	15.34	13.89
2.22	4.44	15.48	13.95
2.23	4.46	15.61	14.01
2.24	4.48	15.76	14.07
2.25	4.5	15.9	14.14
2.26	4.52	16.04	14.2
2.27	4.54	16.18	14.26
2.28	4.56	16.32	14.33
2.29	4.58	16.47	14.39
2.3	4.6	16.61	14.45
2.30	4.6	16.61	14.45
2.31	4.62	16.76	14.51
2.32	4.64	16.9	14.58
2.33	4.66	17.05	14.64
2.34	4.68	17.19	14.7
2.35	4.7	17.34	14.77
2.36	4.72	17.49	14.83
2.37	4.74	17.64	14.89
2.38	4.76	17.79	14.95
2.39	4.78	17.94	15.02
2.4	4.8	18.09	15.08
2.40	4.8	18.09	15.08
2.41	4.82	18.24	15.14
2.42	4.84	18.39	15.2
2.43	4.86	18.54	15.27
2.44	4.88	18.69	15.33
2.45	4.9	18.85	15.39
2.46	4.92	19	15.46
2.47	4.94	19.16	15.52
2.48	4.96	19.31	15.58
2.49	4.98	19.47	15.64
2.5	5	19.63	15.71
2.50	5	19.63	15.71
2.51	5.02	19.78	15.77
2.52	5.04	19.94	15.83
2.53	5.06	20.1	15.9
2.54	5.08	20.26	15.96
2.55	5.1	20.42	16.02
2.56	5.12	20.58	16.08
2.57	5.14	20.74	16.15
2.58	5.16	20.9	16.21
2.59	5.18	21.06	16.27
2.6	5.2	21.23	16.34
2.60	5.2	21.23	16.34
2.61	5.22	21.39	16.4
2.62	5.24	21.55	16.46
2.63	5.26	21.72	16.52
2.64	5.28	21.88	16.59
2.65	5.3	22.05	16.65
2.66	5.32	22.22	16.71
2.67	5.34	22.38	16.78
2.68	5.36	22.55	16.84
2.69	5.38	22.72	16.9
2.7	5.4	22.89	16.96
2.70	5.4	22.89	16.96
2.71	5.42	23.06	17.03
2.72	5.44	23.23	17.09
2.73	5.46	23.4	17.15
2.74	5.48	23.57	17.22
2.75	5.5	23.75	17.28
2.76	5.52	23.92	17.34
2.77	5.54	24.09	17.4
2.78	5.56	24.27	17.47
2.79	5.58	24.44	17.53
2.8	5.6	24.62	17.59
2.80	5.6	24.62	17.59
2.81	5.62	24.79	17.66
2.82	5.64	24.97	17.72
2.83	5.66	25.15	17.78
2.84	5.68	25.33	17.84
2.85	5.7	25.5	17.91
2.86	5.72	25.68	17.97
2.87	5.74	25.86	18.03
2.88	5.76	26.04	18.1
2.89	5.78	26.23	18.16
2.9	5.8	26.41	18.22
2.90	5.8	26.41	18.22
2.91	5.82	26.59	18.28
2.92	5.84	26.77	18.35
2.93	5.86	26.96	18.41
2.94	5.88	27.14	18.47
2.95	5.9	27.33	18.53
2.96	5.92	27.51	18.6
2.97	5.94	27.7	18.66
2.98	5.96	27.88	18.72
2.99	5.98	28.07	18.79
3	6	28.26	18.85
3.00	6	28.26	18.85
3.01	6.02	28.45	18.91
3.02	6.04	28.64	18.97
3.03	6.06	28.83	19.04
3.04	6.08	29.02	19.1
3.05	6.1	29.21	19.16
3.06	6.12	29.4	19.23
3.07	6.14	29.59	19.29
3.08	6.16	29.79	19.35
3.09	6.18	29.98	19.41
3.1	6.2	30.18	19.48