Use this bolt torque chart as a quick reference for common metric and SAE bolt sizes. It is useful for maintenance, early design work, fixture assembly, machine build review, and fastener planning when you need a practical starting point.
For critical joints, always validate against manufacturer recommendations, engineering standards, or tested tightening methods. Torque-only tightening can easily mislead you if friction conditions change.
Metric Bolt Torque Chart (Class 8.8)
| Bolt Size | Torque (Nm) | Torque (ft-lb) |
|---|---|---|
| M5 | 5 | 4 |
| M6 | 10 | 7 |
| M8 | 25 | 18 |
| M10 | 49 | 36 |
| M12 | 85 | 63 |
| M14 | 135 | 100 |
| M16 | 210 | 155 |
| M20 | 410 | 302 |
SAE Bolt Torque Chart (Grade 8)
| Bolt Size | Torque (ft-lb) | Torque (Nm) |
|---|---|---|
| 1/4" | 12 | 16 |
| 5/16" | 25 | 34 |
| 3/8" | 45 | 61 |
| 7/16" | 70 | 95 |
| 1/2" | 110 | 149 |
| 5/8" | 215 | 291 |
| 3/4" | 380 | 515 |
Bolt Torque Calculator
Use the simplified formula below to estimate tightening torque from bolt diameter, clamp load, and friction factor.
K = friction factor, typically around 0.18 to 0.22 for many common conditions
F = clamp load (N)
D = bolt diameter (m)
Need a more complete fastening calculator?
Use the full bolt tightening torque calculator if you want preload-based estimates using property class, stress area, proof load percentage, and assembly condition assumptions.
Open Full Bolt Tightening CalculatorWhy chart torque can be dangerous
Chart values are fast and convenient, but they assume a lot. If lubrication, coating, washer condition, or surface finish changes, the clamp load from the same torque can move a lot. That is why a chart is best for quick reference and starting points, not blind final specs.
The more important the joint is, the less you should rely on a single torque value without validation. Critical or safety-related joints should be reviewed with tested tightening methods, manufacturer data, or a more controlled fastening strategy.