MM to inches calculator

Type millimeters and get inches as a decimal and as the closest mark on a tape measure, or go from inches and fractions to mm.

That's

0.3937 inches

Nearest fraction: 3/8 in
Off by: −0.0187 in (−0.48 mm)
Feet and inches: 3/8 in
Centimeters: 1 cm
Meters: 0.01 m

A + means the fraction is a little longer than the millimeters; − means a little shorter.

How to convert mm to inches

An inch is exactly 25.4 millimeters, by international agreement since 1959. Divide millimeters by 25.4 to get inches; multiply inches by 25.4 to get millimeters.

Inches = millimeters ÷ 25.4
Nearest fraction = inches × 16 (or 8, 32, 64), rounded to a whole number, over 16, then reduced
Millimeters = inches × 25.4
Centimeters = millimeters ÷ 10

Worked example

10 mm ÷ 25.4 = 0.3937 inches. On a tape measure, 0.3937 × 16 = 6.3, which rounds to 6 sixteenths: 3/8 inch. That fraction is 0.475 mm short of 10 mm, so 10 mm is a hair over 3/8. Going back, 1/4 inch is 0.25 × 25.4 = 6.35 mm.

MM to inches chart

Every millimeter from 1 to 25, then common sizes, with the nearest 1/16 and 1/32 inch.

mm	Inches	Nearest 1/16	Nearest 1/32
1 mm	0.0394	1/16	1/32
2 mm	0.0787	1/16	3/32
3 mm	0.1181	1/8	1/8
4 mm	0.1575	3/16	5/32
5 mm	0.1969	3/16	3/16
6 mm	0.2362	1/4	1/4
7 mm	0.2756	1/4	9/32
8 mm	0.315	5/16	5/16
9 mm	0.3543	3/8	11/32
10 mm	0.3937	3/8	13/32
11 mm	0.4331	7/16	7/16
12 mm	0.4724	1/2	15/32
13 mm	0.5118	1/2	1/2
14 mm	0.5512	9/16	9/16
15 mm	0.5906	9/16	19/32
16 mm	0.6299	5/8	5/8
17 mm	0.6693	11/16	21/32
18 mm	0.7087	11/16	23/32
19 mm	0.748	3/4	3/4
20 mm	0.7874	13/16	25/32
21 mm	0.8268	13/16	13/16
22 mm	0.8661	7/8	7/8
23 mm	0.9055	7/8	29/32
24 mm	0.9449	15/16	15/16
25 mm	0.9843	1	31/32
30 mm	1.1811	1 3/16	1 3/16
32 mm	1.2598	1 1/4	1 1/4
35 mm	1.378	1 3/8	1 3/8
40 mm	1.5748	1 9/16	1 9/16
45 mm	1.7717	1 3/4	1 25/32
50 mm	1.9685	1 15/16	1 31/32
60 mm	2.3622	2 3/8	2 3/8
65 mm	2.5591	2 9/16	2 9/16
70 mm	2.7559	2 3/4	2 3/4
75 mm	2.9528	2 15/16	2 15/16
80 mm	3.1496	3 1/8	3 5/32
90 mm	3.5433	3 9/16	3 17/32
100 mm	3.937	3 15/16	3 15/16
120 mm	4.7244	4 3/4	4 23/32
125 mm	4.9213	4 15/16	4 29/32
150 mm	5.9055	5 7/8	5 29/32
200 mm	7.874	7 7/8	7 7/8
250 mm	9.8425	9 13/16	9 27/32
300 mm	11.811	11 13/16	11 13/16
500 mm	19.685	19 11/16	19 11/16
1,000 mm	39.3701	39 3/8	39 3/8

Inches to mm chart

Every 1/32 inch up to an inch, then whole inches to a foot.

Inches	Decimal	mm
1/32 in	0.03125	0.794
1/16 in	0.0625	1.588
3/32 in	0.09375	2.381
1/8 in	0.125	3.175
5/32 in	0.15625	3.969
3/16 in	0.1875	4.763
7/32 in	0.21875	5.556
1/4 in	0.25	6.35
9/32 in	0.28125	7.144
5/16 in	0.3125	7.938
11/32 in	0.34375	8.731
3/8 in	0.375	9.525
13/32 in	0.40625	10.319
7/16 in	0.4375	11.113
15/32 in	0.46875	11.906
1/2 in	0.5	12.7
17/32 in	0.53125	13.494
9/16 in	0.5625	14.288
19/32 in	0.59375	15.081
5/8 in	0.625	15.875
21/32 in	0.65625	16.669
11/16 in	0.6875	17.463
23/32 in	0.71875	18.256
3/4 in	0.75	19.05
25/32 in	0.78125	19.844
13/16 in	0.8125	20.638
27/32 in	0.84375	21.431
7/8 in	0.875	22.225
29/32 in	0.90625	23.019
15/16 in	0.9375	23.813
31/32 in	0.96875	24.606
1 in	1	25.4
2 in	2	50.8
3 in	3	76.2
4 in	4	101.6
5 in	5	127
6 in	6	152.4
7 in	7	177.8
8 in	8	203.2
9 in	9	228.6
10 in	10	254
11 in	11	279.4
12 in	12	304.8

MM to inches questions

How many inches is 10 mm?

0.3937 inches. The nearest sixteenth is 3/8 inch, which is 0.475 mm smaller. 10 mm is 1 cm.

How many inches is 20 mm?

0.7874 inches, or about 13/16 inch to the nearest sixteenth (0.64 mm over). 300 mm, a common metric length, is 11.81 inches, a little under a foot: 11 13/16 in.

What is 1/4 inch in mm?

Exactly 6.35 mm. Other common sizes: 1/8 inch is 3.175 mm, 1/2 inch is 12.7 mm and 3/4 inch is 19.05 mm. Every inch fraction converts to an exact number of millimeters.

What is 3/8 inch in mm?

Exactly 9.525 mm, so a 10 mm wrench or bit is the close metric match (10 mm is 0.3937 in). 5/8 inch is 15.875 mm, close to 16 mm.

How do you convert mm to inches?

Divide by 25.4. For a quick guess in your head, 25 mm is about an inch and 100 mm is about 4 inches (3.94, to be exact). Going the other way, multiply inches by 25.4.

How do I turn mm into a fraction of an inch?

Divide by 25.4, multiply by 16, round to a whole number and put it over 16, then reduce. 6 mm is 0.2362 in, which rounds to 1/4 to the nearest sixteenth or 15/64 to the nearest 1/64. To turn any decimal into a fraction, use the decimal to fraction calculator; to add or subtract lengths, the feet and inches calculator.