The Gasket Torque Calculator helps determine the proper torque to apply to bolts in flange and gasket assemblies. This ensures a secure, leak-proof seal between surfaces in mechanical systems such as pipelines, valves, and pressure vessels. Applying the correct torque is critical to avoid issues like gasket blowout, bolt failure, or flange damage.
This calculator falls under the Mechanical Engineering calculator category. It simplifies the complex process of torque estimation by using recognized engineering formulas that consider material properties, gasket stress, number of bolts, and bolt size. By using this tool, engineers and maintenance professionals can apply the right amount of torque to ensure safety and efficiency in both new installations and routine maintenance operations.
The calculator supports both metric and imperial units, and helps maintain industry-standard practices for bolted flange connections, which are widely used in the oil and gas, water treatment, chemical, and manufacturing industries.
formula
Required Bolt Torque Formula
T = K × F × d
Where:
T = Required bolt torque (in N·m or ft·lb)
K = Nut factor or torque coefficient (typically 0.15 to 0.25, depends on lubrication)
F = Desired bolt preload or clamping force (in N or lbf)
d = Nominal bolt diameter (in meters or inches)
Clamping Force Required (Based on Gasket Seating Stress)
F = Sg × Ag
Where:
F = Total required preload (N or lbf)
Sg = Gasket seating stress (in N/m² or psi)
Ag = Gasket contact area (in m² or in²)
Gasket Contact Area
Ag = π × (D_outer² − D_inner²) / 4
Where:
Ag = Gasket area (in m² or in²)
D_outer = Outer diameter of gasket (in m or in)
D_inner = Inner diameter of gasket (in m or in)
Total Torque for Multiple Bolts
T_total = T × N_bolts
Where:
T_total = Total torque applied across all bolts
T = Torque per bolt
N_bolts = Total number of bolts
Bolt Stress Check (Optional Safety)
σ = F / Ab
Where:
σ = Stress in bolt (N/m² or psi)
F = Load on bolt (N or lbf)
Ab = Tensile stress area of the bolt (m² or in²)
This check helps prevent bolt overloading or failure by ensuring the applied load stays within the bolt’s stress capacity.
Gasket Torque Reference Table
| Parameter | Common Value or Range |
|---|---|
| Nut Factor (K) | 0.15 (lubricated), 0.20–0.25 (dry) |
| Gasket Seating Stress (Sg) | 34.5–69 MPa (5000–10000 psi) |
| Bolt Tensile Stress Area for M16 | 157 mm² |
| Bolt Tensile Stress Area for 5/8″ UNC | 0.226 in² |
| Bolt Torque for M16 (typical) | 90–160 N·m (depends on material) |
| Torque Wrench Unit Conversions | 1 N·m = 0.7376 ft·lb |
| Common Gasket Material (spiral wound) | 34.5 MPa min seating stress |
| Gasket Outer Diameter (example flange) | 150 mm |
| Gasket Inner Diameter (example flange) | 100 mm |
This table offers helpful reference values and conversions for frequent use in gasket torque settings.
Example
You have a gasket with an outer diameter of 150 mm and an inner diameter of 100 mm. The required gasket seating stress is 50 MPa. You’re using M16 bolts with a nominal diameter of 0.016 m, and the nut factor (K) is 0.18. There are 8 bolts.
Step 1: Calculate gasket contact area
Ag = π × (0.15² − 0.10²) / 4 = 0.01227 m²
Step 2: Calculate preload force
F = Sg × Ag = 50,000,000 × 0.01227 = 613,500 N
Step 3: Torque per bolt
T = K × F × d = 0.18 × 613,500 × 0.016 ≈ 1767.84 N·m
Step 4: Total torque for 8 bolts
T_total = T × N_bolts = 1767.84 × 8 = 14,142.72 N·m
So, the total torque required for 8 bolts is approximately 14,142.72 N·m, and each bolt needs 1767.84 N·m.
Most Common FAQs
Proper bolt torque ensures that the gasket compresses evenly and tightly, creating a seal. If torque is too low, leaks can occur. If it’s too high, the gasket or bolts may get damaged.
The nut factor (K) accounts for friction between the bolt, nut, and threads. It directly affects torque calculation. A higher K value means more torque is needed to reach the same preload.
Yes, as long as you know the inner and outer diameters of the gasket, the gasket material stress, and the bolt specifications, this calculator can handle a wide range of gasket sizes and configurations.