Guides / Shop charts · Updated
Wrench size chart
Exact sizes from TEKTON's conversion card. The closest-size columns are our arithmetic, not a maker's claim.
Short answer
Between 1/4 and 1 in, only two inch sizes are close enough to swap with metric: 5/16 in for 8 mm and 3/4 in for 19 mm. Everything else is off by enough to round a bolt head. Use the right system.
SAE to metric
| SAE | Exact mm | Closest mm | Swap? |
|---|---|---|---|
| 1/4 in | 6.350 | 6 mm (+0.35) | No |
| 5/16 in | 7.938 | 8 mm (-0.06) | Yes (TEKTON) |
| 3/8 in | 9.525 | 10 mm (-0.48) | No |
| 7/16 in | 11.112 | 11 mm (+0.11) | No |
| 1/2 in | 12.700 | 13 mm (-0.30) | No |
| 9/16 in | 14.287 | 14 mm (+0.29) | No |
| 5/8 in | 15.875 | 16 mm (-0.13) | No |
| 11/16 in | 17.462 | 17 mm (+0.46) | No |
| 3/4 in | 19.050 | 19 mm (+0.05) | Yes (TEKTON) |
| 13/16 in | 20.637 | 21 mm (-0.36) | No |
| 7/8 in | 22.225 | 22 mm (+0.22) | No |
| 15/16 in | 23.813 | 24 mm (-0.19) | No |
| 1 in | 25.400 | 25 mm (+0.40) | No |
Metric to SAE
| Metric | Inches | Closest SAE |
|---|---|---|
| 6 mm | 0.236 | 1/4 in (+0.35 mm) |
| 7 mm | 0.276 | 1/4 in (-0.65 mm) |
| 8 mm | 0.315 | 5/16 in (-0.06 mm) |
| 9 mm | 0.354 | 3/8 in (+0.52 mm) |
| 10 mm | 0.394 | 3/8 in (-0.48 mm) |
| 11 mm | 0.433 | 7/16 in (+0.11 mm) |
| 12 mm | 0.472 | 1/2 in (+0.70 mm) |
| 13 mm | 0.512 | 1/2 in (-0.30 mm) |
| 14 mm | 0.551 | 9/16 in (+0.29 mm) |
| 15 mm | 0.591 | 9/16 in (-0.71 mm) |
| 16 mm | 0.630 | 5/8 in (-0.13 mm) |
| 17 mm | 0.669 | 11/16 in (+0.46 mm) |
| 18 mm | 0.709 | 11/16 in (-0.54 mm) |
| 19 mm | 0.748 | 3/4 in (+0.05 mm) |
| 20 mm | 0.787 | 13/16 in (+0.64 mm) |
| 21 mm | 0.827 | 13/16 in (-0.36 mm) |
| 22 mm | 0.866 | 7/8 in (+0.22 mm) |
| 23 mm | 0.906 | 7/8 in (-0.78 mm) |
| 24 mm | 0.945 | 15/16 in (-0.19 mm) |
The number in brackets is how much bigger (+) or smaller (−) the other size is. Over about 0.2 mm, a wrench will slip; that cut-off is our suggestion, not a maker's.
More shop charts
Building a bench to use them on? Workbench height calculator.Tap drill chart and drill bit size chart.