Bolt torque calculator
Estimate the order of magnitude of the tightening torque to size the tool. Metric (ISO) and imperial (UN/UNC) fasteners.
Disclaimer — read before use
- The result is purely indicative and only serves to size the tool and recognise an order of magnitude. It is not a tightening specification.
- The tightening torque is a design datum of the joint: it is set by the flange designer, the gasket manufacturer, the plant builder (OEM) or the applicable procedure (e.g. ASME PCC-1, VDI 2230) — not by the tool supplier.
- The actual preload depends on friction, lubrication and thread condition: with torque control alone the scatter is in the order of ±25–30%. Always follow the values and sequence prescribed by the design or the standard.
- Maucotools accepts no liability for the use of the values calculated here.
Pre-filled from the choice above — editable.
Indicative tightening torque
≈ 799 ft·lb
Target preload
328 kN
Yield load
505 kN
Resistant area Aₛ
561.0 mm²
K used
0.11
Rp0.2 900 MPa · D 30 mm · 65% of yield
Indicative value to size the tool — not a tightening specification. Always follow the design datum or the standard (ASME PCC-1 / VDI 2230).
Recommended wrench
MT-HTW-1250
Square drive
3/4"
Torque range
128 – 1,236 Nm
Weight
1.25 kg
Utilisation
88% of range
The model covers the calculated torque. We supply the calibrated hydraulic pump and the torque certificate.
Method: bolt → strength → resistant area → target % → torque (T = K · D · F).
Bolt torque chart for metric bolts (Nm)
Indicative tightening torques for coarse-thread metric bolts from M12 to M64, grades 8.8, 10.9 and 12.9, calculated with the same method as the calculator above (T = K·D·F). For each grade you get the preload and the torque for a dry or zinc-plated bolt and for a bolt lubricated with molybdenum disulphide paste.
- Preload kN
- Nm dry/zinc (K 0.20)
- Nm MoS₂ (K 0.11)
| Size | Grade 8.8 | Grade 10.9 | Grade 12.9 | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Preload kN | Nm dry/zinc (K 0.20) | Nm MoS₂ (K 0.11) | Preload kN | Nm dry/zinc (K 0.20) | Nm MoS₂ (K 0.11) | Preload kN | Nm dry/zinc (K 0.20) | Nm MoS₂ (K 0.11) | |
| M12 | 35 | 84 | 46 | 49 | 118 | 65 | 59 | 142 | 78 |
| M16 | 65 | 209 | 115 | 92 | 294 | 162 | 110 | 353 | 194 |
| M20 | 105 | 420 | 231 | 143 | 573 | 315 | 172 | 688 | 378 |
| M24 | 151 | 727 | 400 | 207 | 991 | 545 | 248 | 1,189 | 654 |
| M30 | 241 | 1,444 | 794 | 328 | 1,969 | 1,083 | 394 | 2,363 | 1,300 |
| M36 | 350 | 2,524 | 1,388 | 478 | 3,441 | 1,893 | 574 | 4,129 | 2,271 |
| M42 | 481 | 4,040 | 2,222 | 656 | 5,509 | 3,030 | 787 | 6,610 | 3,636 |
| M48 | 632 | 6,066 | 3,337 | 862 | 8,272 | 4,550 | 1,034 | 9,927 | 5,460 |
| M56 | 871 | 9,754 | 5,365 | 1,188 | 13,301 | 7,315 | 1,425 | 15,961 | 8,778 |
| M64 | 1,148 | 14,694 | 8,082 | 1,565 | 20,038 | 11,021 | 1,879 | 24,045 | 13,225 |
- Assumptions: preload at 65% of yield load (generic torque-controlled joint); stress area from the coarse metric thread tables; nominal yield 640 MPa for grade 8.8 up to M16 and 660 MPa above, 900 MPa for 10.9, 1,080 MPa for 12.9.
- Lubrication changes the torque by almost a factor of two for the same preload: always use the column that matches the real condition of the bolt.
- Indicative values for sizing the tool: the binding tightening torque is the one in the joint or manufacturer specification (for gasketed flanges the preload is often lower, e.g. 50%). For other cases use the calculator.