You can use this handy chart to quickly convert CM to inches (decimal or fraction).

CM	Inches	Inches
1	0.39	3/8
2	0.79	6/8
3	1.18	1 1/8
4	1.57	1 5/8
5	1.97	2
6	2.36	2 3/8
7	2.76	2 6/8
8	3.15	3 1/8
9	3.54	3 4/8
10	3.94	3 7/8
15	5.91	5 7/8
20	7.87	7 7/8
25	9.84	9 7/8
30	11.81	11 6/8
35	13.78	13 6/8
40	15.75	15 6/8
45	17.72	17 6/8
50	19.69	19 5/8
60	23.62	23 5/8
70	27.56	27 4/8
80	31.50	31 4/8
90	35.43	35 3/8
100	39.37	39 3/8

And to convert inches to centimetres, you can use this simple chart:

Inches	CM
1	2.54
2	5.08
3	7.62
4	10.16
5	12.7
6	15.24
7	17.78
8	20.32
9	22.86
10	25.4
15	38.1
20	50.8
25	63.5
30	76.2
35	88.9
40	101.6
45	114.3
50	127
60	152.4
70	177.8
80	203.2
90	228.6
100	254