| Fractional Inches | Decimal Inches | Millimeters (mm) |
|---|---|---|
| 1/2 | 0.5 | 12.7 |
| 3/8 | 0.375 | 9.53 |
| 5/8 | 0.625 | 15.88 |
| 7/16 | 0.4375 | 11.11 |
| 1/4 | 0.25 | 6.35 |
| 3/4 | 0.75 | 19.05 |
| 7/8 | 0.875 | 22.23 |
| 1 | 1.0 | 25.4 |
| 1/64 | 0.0156 | 0.40 |
| 1/32 | 0.0312 | 0.79 |
| 1/16 | 0.0625 | 1.59 |
| 3/32 | 0.0938 | 2.38 |
| 1/8 | 0.125 | 3.18 |
| 5/32 | 0.1562 | 3.97 |
| 3/16 | 0.1875 | 4.76 |
| 5/16 | 0.3125 | 7.94 |
| 9/16 | 0.5625 | 14.29 |
| 11/16 | 0.6875 | 17.46 |
| 15/16 | 0.9375 | 23.81 |
Why I Rely on Inch-to-MM Conversions in the Shop
I’ve been working on cars for over 25 years, and one thing I’ve learned is that precise measurements really matter. When you’re in the middle of a brake repair or fitting a new suspension component, even the smallest error in converting inches to millimeters can create a lot of extra work later on.
I remember a time early in my career when I made an assumption about a conversion and ended up having to redo a job because things just didn’t fit. That taught me a valuable lesson: 1 inch exactly equals 25.4 millimeters. So, when I work, I know that 1/2 inch is about 12.7 mm, and 3/8 inch comes in at roughly 9.53 mm. These aren’t just numbers from a textbook—they’re the measurements that help me determine the right tools and parts for the job.
Over the years, I’ve always kept a small reference card with these conversions in my glove box. It’s a quick and reliable way to confirm every bolt and fitting is correct on the first try. This habit not only keeps the repairs in line but also saves me a lot of headaches, ensuring every job is done right the first time.
And one more thing: never forget to use the correct tools. Having the right wrench, socket, and gauge not only improves your accuracy but also saves you time and money in the long run. Whether it’s a precise conversion or a tight bolt, the right tools are a mechanic’s best friend.