Having the correct components when carrying out building tasks is crucial to ensure your tasks go smoothly and to plan. If your screws are too short or too long, it’s likely to throw a spanner in the works.
Measuring a screw may seem straightforward, but if you’re not sure which exact part of the screw you need to measure, it may not be so obvious. Our step-by-step guide breaks down how to measure the size of a screw correctly so that you can find the right size parts for your project.
Imperial vs Metric Screw Sizes
Before you start measuring your screw or bolt, you need to know if you’re measuring in metric or imperial units. We recommend using metric units, as the majority of screws are measured in millimetres. But, if for some reason you need to convert your measurements into imperial units, or vice versa, our chart below can help.Imperial vs Metric Screw Size Conversion Chart
METRIC |
IMPERIAL | ||
DIAMETER (MM) | LENGTH (MM) | NOMINAL SIZE (GAUGE) | LENGTH (INCHES) |
3 |
12 | 4 | 1/2 |
3 |
20 | 4 | 3/4 |
3 | 25 | 4 |
1 |
3.5 |
12 | 6 | 1/2 |
3.5 | 16 | 6 |
5/8 |
3.5 |
20 | 6 | 3/4 |
3.5 | 25 | 6 |
1 |
3.5 |
30 | 6 | 11/4 |
4 | 20 | 8 |
3/4 |
4 |
25 | 8 | 1 |
4 | 30 | 8 |
11/4 |
4 |
40 | 8 | 11/2 |
4 | 45 | 8 |
13/4 |
4 |
50 | 8 | 2 |
4 | 60 | 8 |
2 1/2 |
4 |
70 | 8 | 2 3/4 |
5 |
30 | 10 | 11/4 |
5 | 40 | 10 |
11/2 |
5 | 50 | 10 |
2 |
5 |
60 | 10 | 2 1/2 |
5 |
70 | 10 |
2 3/4 |
5 |
80 | 10 |
3 |
5 |
90 | 10 |
3 1/2 |
5 |
100 | 10 |
4 |
6 |
50 | 12 |
2 |
6 |
60 | 12 |
2 1/2 |
6 |
70 | 12 |
2 3/4 |
6 |
80 |
12 |
3 |
6 | 90 | 12 |
3 1/2 |
6 | 100 | 12 |
4 |