Convert inch to millimetre
1 inch = 25.4 millimetres. Enter any value below for an exact conversion.
1 in =
25.4 mm
millimetres
Need the reverse? Convert millimetre to inch →
Formula
1 inch = 25.4 millimetres millimetre = inches × 25.4 inch = millimetres × 0.03937008
inch to millimetre conversion table
1 in25.4 mm
2 in50.8 mm
3 in76.2 mm
5 in127 mm
10 in254 mm
20 in508 mm
25 in635 mm
50 in1270 mm
100 in2540 mm
1000 in25400 mm
About converting inches to millimetres
Inches to millimetres is common in manufacturing and DIY, where imperial drawings need millimetre precision. Multiply inches by 25.4 to get an exact millimetre value.
Frequently asked questions
How many millimetres are in a inch?
One inch equals 25.4 millimetres. So 10 inches is 254 millimetres. Use the converter above for any value.
What is the formula to convert inches to millimetres?
1 inch = 25.4 millimetres millimetre = inches × 25.4 inch = millimetres × 0.03937008
Is the inch-to-millimetre conversion exact?
Yes. The conversion factor between inches and millimetres is defined exactly, so results are precise — only rounded for display.