Skip to main content
Tool Belt Calc

Measure

Torque Conversion Calculator

Convert torque between lb-ft, Nm, lb-in and kgf-m.

Your measurementsEvery assumption editable01
TorqueCalculated live02

Result

135.58Nm

100 lb-ft = 135.58 Nm

Newton-metres
135.582 Nm
Pound-feet
100 lb-ft
Pound-inches
1200 lb-in
Kilogram-metres
13.8255 kgf-m

Pound-feet and foot-pounds are the same unit of torque despite being written both ways. Foot-pounds is also used for energy, which is a different quantity entirely — context is the only thing distinguishing them.

Pound-inches is twelve times pound-feet, and mixing them up is a good way to destroy a small fastener. Torque specs for interior trim and electronics are usually in pound-inches for exactly that reason.

A torque wrench is least accurate at the extremes of its range. A spec near the bottom of a large wrench's scale is better done with a smaller wrench.

Enter a value in whatever unit your spec uses and get all four. The one to watch is pound-inches against pound-feet — a factor of twelve, and the reason small fasteners get destroyed.

Why use this tool?What it does differently03

Why use this tool?

All four units

Pound-feet, newton-metres, pound-inches and kilogram-metres from any starting unit.

Flags the dangerous confusion

Pound-inches is a twelfth of pound-feet. Mixing them up strips threads.

Clears up lb-ft vs ft-lb

Same unit of torque, written both ways. Foot-pounds is also an energy unit, which is a different quantity.

Wrench accuracy noted

A torque wrench is least accurate at the ends of its range.

How this worksThe method04

How this torque conversion calculator works

Everything is normalised to newton-metres first, then converted out. That avoids compounding rounding through a chain of conversions and means all four figures are consistent with each other.

The conversion constants are exact definitions rather than approximations: a pound-foot is 1.3558179483 newton-metres, and a kilogram-metre is 9.80665 by the definition of standard gravity.

Pound-inches is exactly a twelfth of pound-feet. Torque specs for trim, electronics and small fasteners are usually given in pound-inches specifically because the numbers stay readable.

How to use itStep by step05

How to use it

  1. Step 1: Enter the value

    Whatever figure your specification gives.

  2. Step 2: Select its unit

    Getting this wrong by a factor of twelve is the classic error.

  3. Step 3: Read across

    All four equivalents are shown.

  4. Step 4: Check your wrench range

    A spec near the bottom of a large wrench's scale is better done with a smaller one.

Example usageWorked figures06

Example usage

A wheel nut spec
100 lb-ft is 135.58 Nm, 1,200 lb-in, or 13.83 kgf-m.
A metric spec
45 Nm is 33.19 lb-ft — the sort of figure that gets rounded to 33 and is fine, or misread as 45 lb-ft and is not.
A small fastener
25 lb-in is only 2.08 lb-ft. Setting a wrench to 25 lb-ft here would apply twelve times the intended torque.
Frequently asked questionsCommon questions07

Frequently asked questions

How do I convert ft-lb to Nm?

Multiply by 1.3558. One hundred pound-feet is 135.58 newton-metres.

Is ft-lb the same as lb-ft?

For torque, yes — the same unit written either way. Foot-pounds is also used as a unit of energy, which is a different physical quantity that happens to share the name.

How many inch-pounds in a foot-pound?

Exactly twelve. It is the commonest and most damaging torque conversion error, because applying twelve times the intended torque strips almost anything.

Why are small fasteners specified in inch-pounds?

Because the numbers stay readable. A spec of 25 lb-in is easier to work with than 2.08 lb-ft, and small-range wrenches are calibrated in those units.

How accurate is a torque wrench?

Typically within a few per cent across the middle of its range, and noticeably worse at either extreme. Use a wrench whose range puts your target near the middle.

Related toolsElsewhere on the site08

Browse every tool in Measurement & Conversion Calculators.