Millimeters to Inches
Convert millimeters (mm) to inches (in). 1 mm = 0.039370079 in (and 1 in = 25.4 mm). It all runs locally in your browser.
Millimeters to Inches table
| Millimeters | Inches |
|---|---|
| 0.5 mm | 0.019685039 in |
| 1 mm | 0.039370079 in |
| 2 mm | 0.078740157 in |
| 3 mm | 0.11811024 in |
| 5 mm | 0.19685039 in |
| 10 mm | 0.39370079 in |
| 25 mm | 0.98425197 in |
| 50 mm | 1.9685039 in |
| 100 mm | 3.9370079 in |
Where this conversion shows up
This is the workshop conversion. Engineering drawings, 3D-printer dimensions, bolt and socket sizes, camera filter threads and rainfall totals are metric, while many US tools, drill bits and materials are sized in fractional inches. Getting it wrong by a millimeter strips a bolt head.
Worked example
You need an imperial wrench for a 10 mm nut: 10 × 0.0393701 = 0.394 inches — between 3/8″ (0.375) and 13/32″ (0.406). Neither fits well, which is exactly why mixed-unit toolboxes cause skinned knuckles.
Rounding and precision
Machinists work in thousandths of an inch ("thou"): 1 thou = 0.0254 mm. For woodwork, the nearest 1/16″ (1.6 mm) is usually fine. To get fractional inches, multiply the decimal remainder by the denominator you want (0.394 × 32 ≈ 12.6 → 13/32).
How to convert
To convert millimeters to inches, multiply by 0.039370079. Need other units? Use the full Unit Converter.
FAQ
How many inches in a millimeter?
1 millimeter equals 0.039370079 inches (in).
How do I convert millimeters to inches?
Multiply the millimeters value by 0.039370079. For example, 5 mm = 0.19685039 in.
What is 1 mm in fractions of an inch?
1 mm is 0.0394 inches, or just over 1/32″ (0.03125). For quick reference: 3 mm ≈ 1/8″, 6 mm ≈ 1/4″, 13 mm ≈ 1/2″, 25 mm ≈ 1″ — each slightly under.
Are metric and imperial sockets interchangeable?
A few sizes are close enough in a pinch (19 mm ≈ 3/4″ at 19.05 mm), but most are not — a 9/16″ socket on a 14 mm bolt (14.29 vs 14.0) will round the corners. Convert and use the right size.