Length conversion chart

mm, cm, m, in, ft, yd, km, mi

Workshop, drawing, and site lengths using the 1959 international inch and foot. Bookmark the millimetre–inch table for fab work.

When to use: Machining tolerances, architectural dimensions, pipe and fastener callouts, and survey-adjacent site work that still uses feet and miles.

1-unit factor matrix

1 unit equals	mm	cm	m	in	ft	yd	km	mi
Millimetre (mm)	1	0.1	0.001	0.0393701	0.00328084	0.00109361	1.0000e-6	6.2137e-7
Centimetre (cm)	10	1	0.01	0.393701	0.0328084	0.0109361	1.0000e-5	6.2137e-6
Metre (m)	1000	100	1	39.3701	3.28084	1.09361	0.001	0.000621371
Inch (in)	25.4	2.54	0.0254	1	0.0833333	0.0277778	2.5400e-5	1.5783e-5
Foot (ft)	304.8	30.48	0.3048	12	1	0.333333	0.0003048	0.000189394
Yard (yd)	914.4	91.44	0.9144	36	3	1	0.0009144	0.000568182
Kilometre (km)	1000000	100000	1000	39370.1	3280.84	1093.61	1	0.621371
Mile (mi)	1609344	160934	1609.34	63360	5280	1760	1.60934	1

Workshop millimetres

Stock and fastener sizes in inches, centimetres, and metres.

mm	in	cm	m
1	0.0393701	0.1	0.001
2	0.0787402	0.2	0.002
3	0.11811	0.3	0.003
4	0.15748	0.4	0.004
5	0.19685	0.5	0.005
6	0.23622	0.6	0.006
8	0.314961	0.8	0.008
10	0.393701	1	0.01
12	0.472441	1.2	0.012
15	0.590551	1.5	0.015
16	0.629921	1.6	0.016
20	0.787402	2	0.02
25	0.984252	2.5	0.025
25.4	1	2.54	0.0254
30	1.1811	3	0.03
32	1.25984	3.2	0.032
40	1.5748	4	0.04
50	1.9685	5	0.05
75	2.95276	7.5	0.075
100	3.93701	10	0.1
150	5.90551	15	0.15
200	7.87402	20	0.2
250	9.84252	25	0.25
300	11.811	30	0.3
500	19.685	50	0.5
1000	39.3701	100	1

Fractional and whole inches

Drawing inches in millimetres, centimetres, and feet.

in	mm	cm	ft
0.0625	1.5875	0.15875	0.00520833
0.125	3.175	0.3175	0.0104167
0.25	6.35	0.635	0.0208333
0.375	9.525	0.9525	0.03125
0.5	12.7	1.27	0.0416667
0.625	15.875	1.5875	0.0520833
0.75	19.05	1.905	0.0625
1	25.4	2.54	0.0833333
1.5	38.1	3.81	0.125
2	50.8	5.08	0.166667
3	76.2	7.62	0.25
4	101.6	10.16	0.333333
6	152.4	15.24	0.5
8	203.2	20.32	0.666667
10	254	25.4	0.833333
12	304.8	30.48	1
18	457.2	45.72	1.5
24	609.6	60.96	2
36	914.4	91.44	3
48	1219.2	121.92	4
60	1524	152.4	5

Site and storey feet

Architectural and civil feet in metres, inches, and yards.

ft	m	in	yd
1	0.3048	12	0.333333
2	0.6096	24	0.666667
3	0.9144	36	1
4	1.2192	48	1.33333
5	1.524	60	1.66667
6	1.8288	72	2
8	2.4384	96	2.66667
10	3.048	120	3.33333
12	3.6576	144	4
15	4.572	180	5
16	4.8768	192	5.33333
20	6.096	240	6.66667
25	7.62	300	8.33333
30	9.144	360	10
40	12.192	480	13.3333
50	15.24	600	16.6667
75	22.86	900	25
100	30.48	1200	33.3333

1 inch = 25.4 mm exactly. Fractional inches in the lookup table use that exact relationship.
This pack uses the international foot (0.3048 m), not the US survey foot (1200/3937 m). For new US work, NIST retired the survey foot in 2022–2023.
Nautical miles (1 852 m exactly, BIPM) are not included here; use the aviation distance tools for NM.

Defined factors, sources, and methodology

Values match the All Unit Conversions factor library. Exact SI and conventional relationships are preserved; displayed cells are rounded to six significant figures.

Relationship	Status	Note
1 in = 25.4 mm	Exact	International inch, Yard and Pound Agreement (1959). 1 in = 0.0254 m exactly.
1 ft = 0.3048 m	Exact	International foot = 12 × 0.0254 m. This pack does not use the obsolete US survey foot.
1 yd = 0.9144 m	Exact	International yard = 3 international feet.
1 mi = 1 609.344 m	Exact	Statute mile = 5 280 international feet.
1 km = 1 000 m	Exact	SI prefix kilo (10³).
1 Pa = 1 N/m²	Exact	SI derived unit of pressure.
1 bar = 100 000 Pa	Exact	The bar is accepted for use with the SI. 1 bar = 100 kPa exactly.
1 atm = 101 325 Pa	Exact	Standard atmosphere. Distinct from 1 bar (100 000 Pa) and from technical atmosphere (at).
1 Torr = 101 325/760 Pa	Exact	Torr is defined from the standard atmosphere. Close to, but not identical to, 1 mmHg.
1 psi ≈ 6 894.757 Pa	Derived	Pound-force per square inch, derived from the international pound and standard gravity.
1 W = 1 J/s	Exact	SI derived unit of power.
1 kW = 1 000 W	Exact	SI prefix kilo (10³).
1 hp (mechanical) = 745.699872 W	Derived	Mechanical horsepower = 550 ft·lbf/s. Motor nameplates often use this definition.
1 hp (metric) = 735.499 W	Derived	Metric horsepower (PS / cv) ≈ 75 kgf·m/s. Do not mix with mechanical hp on datasheets.

Authority sources

BIPM — The International System of Units (SI Brochure, 9th edition) — Defines the SI base and derived units used in this pack, including the metre, pascal (N/m²), and watt (J/s).
NIST Special Publication 811 — Guide for the Use of the International System of Units (SI) — US guidance for SI usage and conversion factors, including the international inch, foot, yard, and mile.
NIST — SI Units — Plain-language NIST reference for SI base units and common derived engineering units.
NIST — Standard atmosphere (101 325 Pa) — The standard atmosphere is an exact conventional value: 1 atm = 101 325 Pa.

Reviewed 2026-09-13. License: CC BY 4.0. Cite: All Unit Conversions. (2026). Engineering unit conversion chart pack. https://allunitconversions.com/charts/engineering-pack