Bolt Torque Spec Calc

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.