MM to inches converter
Type millimeters or inches and watch both update live.
1 mm = 0.0394 in, so divide millimeters by 25.4 to get inches.
Mm to inches conversion table
| Millimeters | Inches |
|---|---|
| 1 | 0.04 |
| 2 | 0.08 |
| 3 | 0.12 |
| 4 | 0.16 |
| 5 | 0.2 |
| 6 | 0.24 |
| 7 | 0.28 |
| 8 | 0.31 |
| 9 | 0.35 |
| 10 | 0.39 |
| 12 | 0.47 |
| 15 | 0.59 |
| 20 | 0.79 |
| 25 | 0.98 |
| 30 | 1.18 |
| 35 | 1.38 |
| 40 | 1.57 |
| 45 | 1.77 |
| 50 | 1.97 |
| 60 | 2.36 |
| 70 | 2.76 |
| 80 | 3.15 |
| 90 | 3.54 |
| 100 | 3.94 |
- Live two-way conversion
- Exact to 2 decimal places
- Table up to 100 mm
How to convert mm to inches
- Type a value in the millimeters box.
- The inches box updates as you type.
- Check the table for a common part size.
Where a millimeter mismatch matters
A millimeter is a thousandth of a meter, the standard small-scale unit almost everywhere for engineering drawings, screen thickness and tolerances. US hardware stores still sell fasteners in fractional inches, so a bolt, drill bit or socket bought abroad often needs converting before you know if it fits a US thread.
Common tool sizes in mm and inches
| Size | Millimeters | Inches |
|---|---|---|
| Small drill bit | 6 mm | 0.236 in |
| Common drill bit | 12 mm | 0.472 in |
| Socket wrench | 10 mm | 0.394 in |
| Socket wrench | 19 mm | 0.748 in |
A 19 mm socket is close enough to a 3/4 inch (0.75 in) socket that either can sometimes work in a pinch, though the fit is not exact.
A quick way to estimate without a calculator
- Divide millimeters by 25 for a fast estimate. For 19 mm: 19 divided by 25 is 0.76, close to the exact 0.748 inches.
- The shortcut runs a little high since the real factor is 25.4, so treat it as a rough check before ordering a part.
MM to inches FAQ
How many inches is 1 mm?
1 mm equals about 0.04 inches.
How many inches is 25 mm?
25 mm equals 0.98 inches, just under 1 inch.
Why do machinists need this?
Drill bits, screws and sheet metal are often specified in mm on one side and inches on the other, so this checks a fit before ordering.
How precise is the result?
Results show 2 decimal places, accurate enough for most hardware and hobby measurements.
What is a 19 mm socket in inches?
A 19 mm socket is close to a 3/4 inch socket (0.75 in), since 19 mm converts to 0.748 in.
Why do some tools list both mm and fractional inch sizes?
Metric and imperial fasteners are not interchangeable, so tool sets sold in the US often include both a metric socket set in mm and a standard set in fractions of an inch.
How thick is a credit card in inches?
A standard 0.76 mm card is about 0.03 inches thick.
What is an 8 mm bolt in inches?
8 mm is about 0.315 inches, close to but not the same as a 5/16 inch (0.3125 in) bolt, so the two are not always interchangeable.