Convert metric screw size to imperial screw size instantly. Enter a value below, or use the formula and reference table further down the page.
In practice
Metric to imperial screw sizes lines up screw diameters across the two systems. An M3 screw is close to a US #5, M4 to a #8, and M5 to a #10, while M6 is close to 1/4 inch. The diameters are near but the thread pitches are different, so screws from one system will not fit nuts or tapped holes of the other. Use the equivalent for choosing a similar size when shopping, and keep the same system for both parts of any fastener pair.
How to convert metric screw size to imperial screw size
Multiply the value by 1.
inch = M × 1Example: 10 M = 10 inch.
Metric Screw Size to Imperial Screw Size conversion table
| Metric Screw Size (M) | Imperial Screw Size (inch) |
|---|---|
| 1 M | 1 inch |
| 2 M | 2 inch |
| 3 M | 3 inch |
| 4 M | 4 inch |
| 5 M | 5 inch |
| 10 M | 10 inch |
| 15 M | 15 inch |
| 20 M | 20 inch |
| 25 M | 25 inch |
| 50 M | 50 inch |
| 100 M | 100 inch |
Frequently asked questions
How many imperial screw size is 1 metric screw?
1 metric screw equals 1 imperial screw size.
What is the formula to convert M to inch?
To convert M to inch, multiply the value by 1. The full formula is: inch = M × 1.
How do I convert imperial screw size back to metric screw size?
Use the same calculator above and type your value into the imperial screw size field instead — it converts in both directions. Or use the reverse formula: M = inch ÷ 1.
Is the M to inch conversion exact?
The conversion factor used here (1) is the standard internationally defined value. Results on this page are rounded to four decimal places for readability.