You can find the here some formulas and tables about circles: areas and circumferences.
For a circle of diameter d and radius r:
The circumference is πd or 2πr.
The area is πd2/4 or πr2 .
An arc of a circle is part of the circumference.
A tangent to a circle is a straight line which meets the circle at one point only. A radius drawn from the point where a tangent meets a circle is at right angles to the tangent.
A sector of a circle is the area between an arc of the circle and two radii. The area of a sector is 1/2 r²θ, where θ is the angle in radians between the radii. circles: areas and circumferences
A chord is a straight line joining two points on the circumference of a circle. When two chords intersect, the product of the parts of one chord is equal to the products of the parts of the other chord. In the following figure, AE x BE = CE x ED
A segment of a circle is the area bounded by a chord and an arc. Angles in the same segment of a circle are equal: in the following figure, angle A = angle B.
| Diameter | Area | Circumference | Diameter | Area | Circumference | Diameter | Area | Circumference |
| 1 | 0,7854 | 3.142 | 34 | 907,92 | 106,8 | 67 | 3525,7 | 210,5 |
| 2 | 3,1416 | 6.283 | 35 | 962,11 | 110,0 | 68 | 3631,7 | 213,6 |
| 3 | 7,0686 | 9.425 | 36 | 1017,9 | 113,1 | 69 | 3739,3 | 216,8 |
| 4 | 12.566 | 12,57 | 37 | 1075,2 | 116,2 | 70 | 3848,5 | 219,9 |
| 5 | 19.635 | 15,71 | 38 | 1134,1 | 119,4 | 71 | 3959,2 | 223,1 |
| 6 | 28.274 | 18,85 | 39 | 1194,6 | 122,5 | 72 | 4071,5 | 226,2 |
| 7 | 38.485 | 21,99 | 40 | 1256,6 | 125,7 | 73 | 4185,4 | 229,3 |
| 8 | 50.265 | 25,13 | 41 | 1320,3 | 128,8 | 74 | 4300,8 | 232,5 |
| 9 | 63.617 | 28,27 | 42 | 1385,4 | 131,9 | 75 | 4417,9 | 235,6 |
| 10 | 78.540 | 31,42 | 43 | 1452,2 | 135,1 | 76 | 4536,5 | 238,8 |
| 11 | 95.033 | 34,56 | 44 | 1520,5 | 138,2 | 77 | 4656,6 | 241,9 |
| 12 | 113,10 | 37,70 | 45 | 1590,4 | 141,4 | 78 | 4778,4 | 245,0 |
| 13 | 132,73 | 40,84 | 46 | 1661,9 | 144,5 | 79 | 4901,7 | 248,2 |
| 14 | 153,94 | 43,98 | 47 | 1734,9 | 147,7 | 80 | 5026,5 | 251,3 |
| 15 | 176,71 | 47,12 | 48 | 1809,6 | 150,8 | 81 | 5153,0 | 254,5 |
| 16 | 201,06 | 50,27 | 49 | 1885,7 | 153,9 | 82 | 5381,0 | 257,6 |
| 17 | 226,98 | 53,41 | 50 | 1963,5 | 157,1 | 83 | 5410,6 | 260,8 |
| 18 | 254,47 | 56,55 | 51 | 2042,8 | 160,2 | 84 | 5541,8 | 263,9 |
| 19 | 283,53 | 59,69 | 52 | 2123,7 | 163,4 | 85 | 5674,5 | 267,0 |
| 20 | 314,16 | 62,83 | 53 | 2206,2 | 166,5 | 86 | 5808,8 | 270,2 |
| 21 | 346,36 | 65,97 | 54 | 2290,2 | 169,6 | 87 | 5944,7 | 273,3 |
| 22 | 380,13 | 69,11 | 55 | 2375,8 | 172,8 | 88 | 6082,1 | 276,5 |
| 23 | 415,48 | 72,26 | 56 | 2463,0 | 175,9 | 89 | 6221,1 | 279,6 |
| 24 | 452,39 | 75,40 | 57 | 2551,8 | 179,1 | 90 | 6361,7 | 282,7 |
| 25 | 490,87 | 78,54 | 58 | 2642,1 | 182,2 | 91 | 6503,9 | 285,9 |
| 26 | 530,93 | 81,68 | 59 | 2734,0 | 185,4 | 92 | 6647,6 | 289,0 |
| 27 | 572,56 | 84,82 | 60 | 2827,4 | 188,4 | 93 | 6792,9 | 292,2 |
| 28 | 616,75 | 87,96 | 61 | 2922,5 | 191,6 | 94 | 6939,8 | 295,3 |
| 29 | 660,52 | 91,11 | 62 | 3019,1 | 194,8 | 95 | 7088,2 | 298,5 |
| 30 | 706,86 | 94,25 | 63 | 3117,2 | 197,9 | 96 | 7238,2 | 301,6 |
| 31 | 754,77 | 97,39 | 64 | 3217,0 | 201,1 | 97 | 7389,8 | 304,7 |
| 32 | 804,25 | 100,5 | 65 | 3318,3 | 204,2 | 98 | 7543,0 | 307,9 |
| 33 | 855,30 | 103,7 | 66 | 3421,2 | 207,3 | 99 | 7697,7 | 311,0 |