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mm to inches
Convert millimeters to inches using 1 inch = 25.4 mm exactly.
1 millimeter equals 0.03937 inches. This free mm to inches converter divides millimeters by 25.4 because one inch is exactly 25.4 mm. That is the same definition behind cm to inches. Use it for tool sizes, phone specs, jewelry, and any fine metric dimension that needs an inch reading in the US. Small parts change meaning fast, so an exact factor matters.
How to convert mm to inches
Divide millimeters by 25.4. In short: inches = mm ÷ 25.4.
Example: 25 mm ÷ 25.4 = 0.98 inches. So 25 millimeters is 0.98 inches.
This is the same definition used for centimeters, because 10 mm equals 1 cm. Small values need careful rounding at two decimals.
mm to inches conversion chart
Common millimeter values converted to inches, rounded to two decimal places.
| Millimeters (mm) | Inches (in) |
|---|---|
| 1 mm | 0.04 in |
| 2 mm | 0.08 in |
| 3 mm | 0.12 in |
| 4 mm | 0.16 in |
| 5 mm | 0.2 in |
| 10 mm | 0.39 in |
| 15 mm | 0.59 in |
| 20 mm | 0.79 in |
| 25 mm | 0.98 in |
| 30 mm | 1.18 in |
| 40 mm | 1.57 in |
| 50 mm | 1.97 in |
| 75 mm | 2.95 in |
| 100 mm | 3.94 in |
For drill bits and jewelry sizes, compare the chart first when you only need a common value.
Common mm to inches conversions
1 mm is 0.04 inches. 5 mm is 0.20 inches. Hardware and craft parts use these often.
10 mm is 0.39 inches. 25 mm is 0.98 inches, almost exactly one inch.
50 mm is 1.97 inches. 100 mm is 3.94 inches, the same as 10 cm.
When a spec lists both mm and inches, confirm they match this factor before you buy parts.
Phone thickness and lens filters are often metric. Convert when a US accessory list is only in inches.
Why US makers still convert mm to inches
Precision products worldwide are labeled in millimeters. US tools, print, and DIY guides still talk in fractions of an inch.
Converting mm to inches lets you match drill bits, phone sizes, and packaging notes without guessing. It keeps metric detail while speaking in US units.
For shop notes, convert once and keep the inch value next to the original mm value. That audit trail avoids rework.
Engineering drawings may list mm only. Convert critical gaps before you cut US stock sold in inches.
Frequently asked questions
How many inches is 1 mm?
1 mm equals about 0.03937 inches, or 0.04 inches rounded to two decimals.
How many inches is 10 mm?
10 mm equals 0.39 inches.
How many inches is 25 mm?
25 mm equals 0.98 inches, nearly 1 inch.
How many inches is 50 mm?
50 mm equals 1.97 inches.
Is 25.4 mm exactly one inch?
Yes. One inch is defined as exactly 25.4 millimeters.
More free converters
Also try cm to inches and inches to cm. All length units live on the length converter hub.
See NIST - SI units for length for official length unit context.