Inches to MM Converter
Updated Formulas shown
Multiply inches by 25.4 to get millimeters: 1 in = 25.4 mm exactly, 3/4″ = 19.05 mm. Fractions such as 23/32 or 1 1/2 can be typed as-is.
Formula: millimeters = inches × 25.4 (exact)
Common values: inches → millimeters
| inches | millimeters |
|---|---|
| 25.4 mm | |
| 50.8 mm | |
| 76.2 mm | |
| 127 mm | |
| 254 mm | |
| 508 mm | |
| 635 mm | |
| 1,270 mm | |
| 2,540 mm | |
| 6,350 mm | |
| 12,700 mm | |
| 25,400 mm |
1 in in every length unit
- 25.4 mm
- 2.54 cm
- 0.0254 m
- 0.0000254 km
- 0.0833333 ft
- 0.0277778 yd
- 0.0000157828 mi
- 1,000 mil
- 25,400 µm
- 0.0000137149 nmi
How to convert inches to millimeters
- Type the value in inches into the converter (or into the right-hand box to go the other way).
- Multiply by 25.4 to get millimeters.
- Round to a sensible precision with the Decimals control; the table below covers the values people look up most.
Inch to millimeter formula
millimeters = inches × 25.4 — 1 in = 25.4 mm. The factor is exact by definition (NIST SP 811), so any rounding comes only from how many decimals you keep.
in to mm conversion table
Inch fraction to millimeter chart
| inches | decimal | mm |
|---|---|---|
| 1/64″ | 0.015625 | 0.397 |
| 1/32″ | 0.03125 | 0.794 |
| 3/64″ | 0.046875 | 1.191 |
| 1/16″ | 0.0625 | 1.588 |
| 5/64″ | 0.078125 | 1.984 |
| 3/32″ | 0.09375 | 2.381 |
| 7/64″ | 0.109375 | 2.778 |
| 1/8″ | 0.125 | 3.175 |
| 9/64″ | 0.140625 | 3.572 |
| 5/32″ | 0.15625 | 3.969 |
| 11/64″ | 0.171875 | 4.366 |
| 3/16″ | 0.1875 | 4.762 |
| 13/64″ | 0.203125 | 5.159 |
| 7/32″ | 0.21875 | 5.556 |
| 15/64″ | 0.234375 | 5.953 |
| 1/4″ | 0.25 | 6.35 |
| 17/64″ | 0.265625 | 6.747 |
| 9/32″ | 0.28125 | 7.144 |
| 19/64″ | 0.296875 | 7.541 |
| 5/16″ | 0.3125 | 7.938 |
| 21/64″ | 0.328125 | 8.334 |
| 11/32″ | 0.34375 | 8.731 |
| 23/64″ | 0.359375 | 9.128 |
| 3/8″ | 0.375 | 9.525 |
| 25/64″ | 0.390625 | 9.922 |
| 13/32″ | 0.40625 | 10.319 |
| 27/64″ | 0.421875 | 10.716 |
| 7/16″ | 0.4375 | 11.112 |
| 29/64″ | 0.453125 | 11.509 |
| 15/32″ | 0.46875 | 11.906 |
| 31/64″ | 0.484375 | 12.303 |
| 1/2″ | 0.5 | 12.7 |
| 33/64″ | 0.515625 | 13.097 |
| 17/32″ | 0.53125 | 13.494 |
| 35/64″ | 0.546875 | 13.891 |
| 9/16″ | 0.5625 | 14.288 |
| 37/64″ | 0.578125 | 14.684 |
| 19/32″ | 0.59375 | 15.081 |
| 39/64″ | 0.609375 | 15.478 |
| 5/8″ | 0.625 | 15.875 |
| 41/64″ | 0.640625 | 16.272 |
| 21/32″ | 0.65625 | 16.669 |
| 43/64″ | 0.671875 | 17.066 |
| 11/16″ | 0.6875 | 17.463 |
| 45/64″ | 0.703125 | 17.859 |
| 23/32″ | 0.71875 | 18.256 |
| 47/64″ | 0.734375 | 18.653 |
| 3/4″ | 0.75 | 19.05 |
| 49/64″ | 0.765625 | 19.447 |
| 25/32″ | 0.78125 | 19.844 |
| 51/64″ | 0.796875 | 20.241 |
| 13/16″ | 0.8125 | 20.638 |
| 53/64″ | 0.828125 | 21.034 |
| 27/32″ | 0.84375 | 21.431 |
| 55/64″ | 0.859375 | 21.828 |
| 7/8″ | 0.875 | 22.225 |
| 57/64″ | 0.890625 | 22.622 |
| 29/32″ | 0.90625 | 23.019 |
| 59/64″ | 0.921875 | 23.416 |
| 15/16″ | 0.9375 | 23.813 |
| 61/64″ | 0.953125 | 24.209 |
| 31/32″ | 0.96875 | 24.606 |
| 63/64″ | 0.984375 | 25.003 |
| 1″ | 1 | 25.4 |
Actual lumber sizes in millimeters
| nominal | actual (in) | actual (mm) |
|---|---|---|
| 1×4 | 3/4″ × 3 1/2″ | 19 × 89 mm |
| 1×6 | 3/4″ × 5 1/2″ | 19 × 140 mm |
| 2×4 | 1 1/2″ × 3 1/2″ | 38 × 89 mm |
| 2×6 | 1 1/2″ × 5 1/2″ | 38 × 140 mm |
| 2×8 | 1 1/2″ × 7 1/4″ | 38 × 184 mm |
| 2×10 | 1 1/2″ × 9 1/4″ | 38 × 235 mm |
| 2×12 | 1 1/2″ × 11 1/4″ | 38 × 286 mm |
| 4×4 | 3 1/2″ × 3 1/2″ | 89 × 89 mm |
| 6×6 | 5 1/2″ × 5 1/2″ | 140 × 140 mm |
Actual dry sizes per the American Softwood Lumber Standard (PS 20). Pressure-treated lumber can be slightly larger when wet.
Framing and sheet sizes in metric
US studs at 16″ on center are 406.4 mm apart and 24″ spacing is 609.6 mm; metric framing uses 400 and 600 mm. A 4 × 8 ft sheet of drywall or plywood is 1,219 × 2,438 mm, while metric sheets are 1,200 × 2,400 mm — so metric sheets don't land on US stud layouts without trimming.
When you are reading a metric drawing, it helps to convert the whole dimension first and only then round to a tape-measure fraction, rather than rounding each piece and adding the errors up.
Related converters & calculators
- MM to Inches ConverterDivide by 25.4, plus metric-to-SAE socket sizes.
- Inches to CM ConverterMultiply by 2.54 — fractions like 3 1/2 work too.
- Board Foot CalculatorBoard feet and cost for a full lumber list.
- Stud CalculatorCalculate wall studs at 12, 16 or 24 inches on center, plus extras for corners and openings and plate lumber.
- CM to Inches ConverterDivide by 2.54, with tape-measure fractions.
- Feet to Meters ConverterMultiply by 0.3048 (exact).
- Meters to Feet ConverterDivide by 0.3048, shown in feet and inches.
- CM to Feet and Inches ConverterHeight in cm to feet and inches.
Frequently asked questions
How many mm is 3/4 inch?
3/4″ = 19.05 mm. 23/32″ (the actual thickness of most "3/4" plywood) is 18.26 mm.
What is a 2×4 in mm?
A dry 2×4 actually measures 1 1/2″ × 3 1/2″, which is 38 × 89 mm.
How many mm in 1/8 inch?
1/8″ = 3.175 mm.
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Estimates only. Check quantities with your supplier or contractor before ordering.