mm to Inches Converter

mm to in conversion chart

Calculated with the formula above; filter or export as CSV.

Filter chart

mm to in conversion chart
mm	in	cm	Nearest inch fraction
0.5	0.01968504	0.05	1/64"
1	0.03937008	0.1	3/64"
1.5	0.05905512	0.15	1/16"
2	0.07874016	0.2	5/64"
3	0.11811024	0.3	1/8"
4	0.15748031	0.4	5/32"
5	0.19685039	0.5	13/64"
6	0.23622047	0.6	15/64"
8	0.31496063	0.8	5/16"
10	0.39370079	1.0	25/64"
12	0.47244094	1.2	15/32"
15	0.59055118	1.5	19/32"
16	0.62992126	1.6	5/8"
19	0.7480315	1.9	3/4"
20	0.78740157	2.0	25/32"
22	0.86614173	2.2	55/64"
25	0.98425197	2.5	63/64"
25.4	1.0	2.54	1"
30	1.18110236	3.0	1 3/16"
32	1.25984252	3.2	1 17/64"
40	1.57480315	4.0	1 37/64"
50	1.96850394	5.0	1 31/32"
60	2.36220472	6.0	2 23/64"
75	2.95275591	7.5	2 61/64"
100	3.93700787	10.0	3 15/16"
150	5.90551181	15.0	5 29/32"
200	7.87401575	20.0	7 7/8"
300	11.81102362	30.0	11 13/16"
500	19.68503937	50.0	19 11/16"
1000	39.37007874	100.0	39 3/8"

Formula and method

in = mm × 0.039370079 mm = in × 25.4 Multiply by the source unit’s SI factor to get m, then divide by the target unit’s SI factor.

Worked example

10 mm × 0.039370079 = 0.3937 in.

Assumptions and limits

1 in = 25.4 mm is exact by definition; the fraction is the nearest 1/64" and is unrelated to nominal pipe sizes (NPS).
Results show up to 4 decimals; Copy and CSV keep more digits.

Frequently asked questions

How many in are in 1 mm?

1 mm = 0.039370079 in. The factor follows from the SI definitions: 1 in = 25.4 mm exactly (1959 international agreement).

How do I convert in back to mm?

Multiply by 25.4 (or divide by 0.039370079), or simply switch “From unit” to in. For example 10 in = 254 mm.

How is the inch fraction (like 3/8") worked out?

Divide mm by 25.4 for decimal inches, then round to the nearest 1/64 and reduce. For example 10 mm = 0.3937", × 64 = 25.2, so 25/64"; 9.525 mm is exactly 3/8". The page flags when the fraction is rounded — use the decimal for precision work.

References

mm to Inches Converter practical guide and common questions

What does mm to Inches Converter calculate?

Convert millimetres to inches — as a decimal and as the nearest 1/64" fraction — plus centimetres, feet and metres, with a chart of common sizes. Conversion runs in your browser; factors are from NIST SP 811. in = mm × 0.039370079 mm = in × 25.4 Multiply by the source unit’s SI factor to get m, then divide by the target unit’s SI factor.

When is this useful?

10 mm × 0.039370079 = 0.3937 in.

How do I enter the inputs?

Enter the inputs for mm to Inches Converter: Value, From unit. Calculate, check the units and assumptions, then copy or download the results.

How should I interpret the results?

1 in = 25.4 mm is exact by definition; the fraction is the nearest 1/64" and is unrelated to nominal pipe sizes (NPS). Results show up to 4 decimals; Copy and CSV keep more digits.

Where are my inputs processed?

mm to Inches Converter runs in this browser. Inputs are not uploaded to a calculation server; copying and CSV download require your action. The existing site analytics and advertising still load.