1 Inches to mm
1 in = 25.4 mm
1 inch equals 25.4 millimeters.
How to convert 1 in to mm
Use the formula mm = in × 25.4:
mm = 1 × 25.4mm = 25.4
So 1 in = 25.4 mm.
Rounded values and quick estimate
- Rounded to a whole number: 25 mm
- Rounded to one decimal place: 25.4 mm
- Conversion factor: 1 inch = 25.4 millimeters
This conversion is exact, so there is no need to estimate: just multiply by 25.4.
1 Inches in other units
- Millimeters
- 25.4 mm
- Centimeters
- 2.54 cm
- Meters
- 0.0254 m
- Kilometers
- 0.000025 km
- Feet
- 0.0833 ft
- Yards
- 0.0278 yd
- Miles
- 0.000016 mi
- Micrometers
- 25400 µm
- Hands
- 0.25 hh
- Nautical miles
- 0.000014 nmi
- Mils (thou)
- 1000 mil
1 in and nearby values
About inches and millimeters
An inch is defined as exactly 2.54 centimeters. There are 12 inches in a foot; inches are used in the US for screens, heights and small lengths.
A millimeter is one thousandth of a meter (0.1 cm). It is used for small, precise measurements like rainfall, screws and paper thickness.
Related conversions
Frequently asked questions
What is 1 Inches in mm?
1 inch is 25.4 millimeters (1 in = 25.4 mm).
How do you convert 1 in to mm?
Apply mm = in × 25.4: mm = 1 × 25.4, mm = 25.4.
How many inches is 25.4 mm?
25.4 mm is about 1 inch.