How to use the Torque Converter
- Enter the torque value from your specification or wrench.
- Select the source unit — check whether it is pound-feet or pound-inches, they differ twelvefold.
- Select the unit your tool is calibrated in.
- Apply the converted figure with a calibrated wrench, tightening smoothly rather than in jerks.
- Follow the manufacturer's sequence and any specified stages rather than going straight to the final value.
How the calculation works
Torque is force applied at a distance from an axis, so its units are always a force unit multiplied by a length unit. The SI unit is the newton-metre. It is dimensionally identical to the joule but conceptually distinct — a joule is energy delivered, a newton-metre of torque is a twisting effort that may deliver no energy at all if nothing rotates. Convention keeps them typographically separate to avoid exactly that confusion.
Pound-feet and pound-inches are both common and are a factor of twelve apart, which makes mixing them a genuinely dangerous error. Small fasteners, electronics and instrumentation are usually specified in pound-inches or newton-centimetres; wheel nuts and engine bolts in pound-feet or newton-metres. A wheel nut spec of 100 lb-ft applied as 100 lb-in would leave the nut barely finger-tight.
Torque is a proxy for clamping force, not the goal itself. Only around 10 to 15% of applied torque becomes bolt tension; the rest is lost to friction under the head and in the threads. That is why lubrication changes the required figure substantially, why manufacturers specify dry or lubricated conditions, and why critical joints increasingly use torque-plus-angle or direct tension measurement rather than torque alone.
torque_target = (T_source × Nm_per_source) ÷ Nm_per_target; 1 lb-ft = 1.3558179 N·m; 1 lb-in = lb-ft ÷ 12 = 0.1129848 N·m; 1 kgf·m = 9.80665 N·mSource: ISO 80000-4; NIST Special Publication 811; ISO 16047 fastener torque/clamp-force testing.
Worked example
A service manual specifies 90 N·m for wheel bolts and your torque wrench reads in pound-feet.
- Enter 90 and select newton-metres.
- Convert to pound-feet: 90 ÷ 1.3558179 = 66.4 lb-ft.
- Set the wrench to 66 or 67 lb-ft.
- Tighten in a star pattern in two stages, roughly 50% then full, and re-check after a short drive.
90 N·m is 66.4 lb-ft — set the wrench to 66 lb-ft and use a star pattern rather than a single pass.
Frequently asked questions
Is pound-foot the same as foot-pound?+
In practice the two names are used interchangeably for torque, though strictly foot-pound describes energy and pound-foot describes torque.
How many newton-metres is one pound-foot?+
1.3558 N·m. A useful mental shortcut is that N·m figures are about 1.36 times the pound-foot number.
Why do lubricated and dry torque specs differ?+
Lubrication cuts friction, so the same torque produces much higher bolt tension. Using a dry spec on lubricated threads can over-stretch or snap the fastener.
Does a torque wrench need calibrating?+
Yes, typically annually or every few thousand cycles. Always wind a click-type wrench back to its lowest setting for storage.
Last reviewed September 1, 2026. We review this page whenever the underlying formula, tax year, published rate or standard changes.