UnitConvConvert
Length

Convert millimeters to inches

1 mm=0.03937in

Use the converter below to change any millimeters value into inches instantly — with formula, conversion table, and real-world examples.

0.03937

Conversion formula

Forward
inches = millimeters × 0.03937
Reverse
millimeters = inches × 25.4

Example: 10 mm × 0.03937 = 0.3937 in.

About both units

From

Millimeter

mm

The millimeter equals one thousandth of a meter and is essential in precision engineering, manufacturing and rainfall measurement. A 10-millimetre rainfall is a moderate shower; over 50 mm in a day is classified as heavy. Machined parts, screws and PCB dimensions are all given in mm.

Real-world: A 2 euro coin is 25.75 mm across and 2.2 mm thick. Rainfall of 50 mm in 24 h is a red-warning event in most of Europe.
Read full millimeter reference →
To

Inch

in

The inch equals 2.54 centimeters exactly since 1959. It is the global standard for screen diagonal sizes — a "55-inch TV" has a 139.7 cm diagonal. Pipe diameters, US and UK shoe sizes, and hard-drive form factors are all specified in inches. 1 inch = 1/12 foot = 1/36 yard.

Real-world: A 65-inch TV has a 165 cm diagonal. A smartphone screen is typically 6–7 inches. Standard copper plumbing in the UK is ½ inch or ¾ inch.
Read full inch reference →

Millimeter to Inch conversion table

Common millimeters to inches values for quick reference.

Millimeter (mm)Inch (in)
1 mm0.03937 in
5 mm0.1969 in
10 mm0.3937 in
25 mm0.9843 in
50 mm1.9685 in
100 mm3.93701 in
250 mm9.84252 in
500 mm19.685 in
1,000 mm39.3701 in
5,000 mm196.85 in

Tips & common mistakes

Quick tips

  • 1 mm is the smallest graduation on a standard ruler. 10 mm = 1 cm exactly.
  • Rainfall in mm is depth — 25 mm of rain over 1 m² equals 25 litres of water.
  • For very small measurements switch to micrometres (µm) — 1 mm = 1000 µm.

Avoid these

  • Reading an engineering drawing dimensioned in mm as if it were cm — a factor-of-10 error.
  • Using 25 instead of 25.4 when converting mm to inches — the error matters in CNC machining.
  • Confusing millimetre (length) with millilitre (volume) — both abbreviated with "ml" but on different scales.

Frequently asked questions

How many inches in a millimeter?
One millimeter equals 0.03937 inches.
How do I convert millimeters to inches?
Multiply the millimeter value by 0.03937 to get the equivalent in inches.
What is 100 millimeters in inches?
100 millimeters equals 3.93701 inches.
Is a millimeter bigger than a inch?
No. 1 millimeter equals 0.03937 inches, so one millimeter is smaller.
How to convert millimeters to inches without a calculator?
Multiply by 0.04 for a quick estimate; use a calculator for precise results.

Related length conversions

📊 See full comparison matrix →

More from Millimeter

mm → m
1 = 0.001 m
mm → km
1 = 1.0000e-6 km
mm → cm
1 = 0.1 cm
mm → mi
1 = 6.2137e-7 mi
mm → yd
1 = 0.001094 yd
mm → ft
1 = 0.003281 ft
mm → nmi
1 = 5.3996e-7 nmi
mm → µm
1 = 1,000 µm

More to Inch

m → in
1 = 39.3701 in
km → in
1 = 39,370.08 in
cm → in
1 = 0.3937 in
mi → in
1 = 63,360 in
yd → in
1 = 36 in
ft → in
1 = 12 in
nmi → in
1 = 72,913.39 in
µm → in
1 = 3.9370e-5 in

Conversions in other categories

WeightKilogram → PoundTemperatureCelsius → FahrenheitVolumeLiter → US GallonAreaSquare Meter → Square FootSpeedKilometer per Hour → Mile per HourEnergyKilojoule → KilocaloriePressureBar → Pound per Square InchPowerKilowatt → Mechanical Horsepower