Bolt Torque Spec Calc

5/8-inch Grade 8 stud, lubricated - 175 ft-lb dry, 131 lubed. SAE grades 2/5/8 + metric 4.6/8.8/10.9/12.9. 28 SAE sizes, 17 metric. $1.99 one-time.

Built for mechanics, millwrights, and equipment installers who need bolt torque on the bench - not a desktop tool.

WHAT IT DOES Looks up torque values for standard bolt sizes and grades using the T = K x D x F formula with K = 0.20. SAE grades 2, 5, and 8 across 28 sizes from #6-32 to 1-1/2 inch. Metric classes 4.6, 8.8, 10.9, and 12.9 across 17 sizes from M3 to M36. Dry vs. lubricated multiplier applied to the result.

INPUTS

• Standard: SAE or Metric
• Bolt size (28 SAE or 17 metric sizes available)
• Bolt grade or class
• Lube condition: Dry or Lubricated

RETURNS

• Torque in ft-lb
• Torque in N·m

CALCULATION BASIS

• Torque formula: T = 0.20 x D x F
• Preload F = 75% of proof strength times tensile stress area
• Lubricated multiplier: 0.75 times the dry value

WHY THIS APP, NOT THE FREE ONES

• Math is shown - formula and assumed K factor visible, not hidden.
• 45 size and grade combinations covered in one tap.
• Works offline - shop floor, field repair, no Wi-Fi. Always available.
• No login. No ads. No telemetry. No subscription.

PRICING $1.99. Pay once, own it. Lifetime access on iPhone, iPad, and Mac via Family Sharing.

NOT A SUBSTITUTE FOR Manufacturer-specified torque values for safety-critical fasteners. Calibrated wrench certificates. Specific K-factor adjustments for anti-seize, plating, or galvanized threads - this app uses K = 0.20 for both dry and lubricated, with the 0.75x multiplier as the only lube adjustment. Verify against the OEM tightening spec for the specific application.