About Torque Unit Converter — Nm, ft-lb, in-lb & kgf·m
The torque unit converter translates a torque (a moment — force times lever arm) between the units that fastener specs, motor datasheets, and service manuals mix constantly: newton-meters from metric documentation, foot-pounds from US torque wrenches, inch-pounds from small-fastener and aviation specs, and kgf·m or kgf·cm from older metric equipment and Japanese service literature. Every conversion runs through the SI unit — the newton-meter — using NIST SP 811 Appendix B factors: 1 ft·lbf = 1.355818 N·m and 1 kgf·m = 9.80665 N·m exactly.
The anchors worth memorizing: 1 ft·lb ≈ 1.356 N·m (so N·m values are about 35% bigger than ft·lb values for the same torque), 1 ft·lb = 12 in·lb exactly, and 1 kgf·m ≈ 9.807 N·m ≈ 7.233 ft·lb. Torque is a signed quantity — tightening versus loosening, or opposite moment directions in a free-body diagram — so negative entries convert normally instead of erroring.
How It Works
- Enter the torque value, pick the unit it is currently in ("from"), and pick the unit you need ("to"). The headline shows the converted value; the table beneath shows the same torque in all six units at once.
- Every conversion is value × (N·m per from-unit) ÷ (N·m per to-unit). kgf·m and kgf·cm are exact (the standard gravity 9.80665 m/s² is a definition); ft·lbf and in·lbf carry the published NIST 7-significant-figure values, and their 12:1 ratio is exact because both come from the same pound-force.
- Displayed values are rounded to 6 significant digits; the conversion itself runs in full double precision, so converting back returns your original number.
- Watch the classic spec-sheet trap: in·lb versus ft·lb. A fastener spec of 89 in·lb is only 7.4 ft·lb — setting a wrench to 89 ft·lb instead is a 12× over-torque that strips threads. When a number seems suspiciously high or low, convert it and sanity-check the units first.
Worked Example
A lug-nut spec reads 100 ft·lb and the only torque wrench on hand is metric. Through the base unit: 100 ft·lb × 1.355818 N·m/ft·lb = 135.582 N·m — set the wrench to 135 N·m and the joint is within a fraction of a percent of spec. The same torque is 1,200 in·lb exactly (12 in·lb per ft·lb) and 13.8255 kgf·m; going the other way, the chart's "100 N·m" row shows 73.7562 ft·lb.
Nm to ft-lbs conversion chart (with in-lb and kgf·m)
Common metric torque specs converted with the NIST SP 811 factors (1 ft·lbf = 1.355818 N·m; 1 kgf·m = 9.80665 N·m exact), shown to 6 significant digits — exactly what the converter outputs for the same inputs.
| Torque | ft·lb | in·lb | kgf·m |
|---|---|---|---|
| 10 N·m (small fastener) | 7.37562 | 88.5075 | 1.01972 |
| 25 N·m (spark plug) | 18.4391 | 221.269 | 2.54929 |
| 50 N·m (M10 class 8.8) | 36.8781 | 442.537 | 5.09858 |
| 80 N·m (M12 class 8.8) | 59.005 | 708.06 | 8.15773 |
| 100 N·m (lug nut, small car) | 73.7562 | 885.075 | 10.1972 |
| 150 N·m (lug nut, truck) | 110.634 | 1,327.61 | 15.2957 |
Formulas
- Conversion through the base unit
x = value × f_from ÷ f_to- N·m per unit (the factor table)
ft·lbf 1.355818 · in·lbf 0.1129848 · kgf·m 9.80665 · kgf·cm 0.0980665 · kN·m 10³- The everyday anchors
1 ft·lb ≈ 1.35582 N·m; 1 ft·lb = 12 in·lb (exact); 1 kgf·m ≈ 7.23301 ft·lb
Standards & References
- NIST SP 811, Guide for the Use of the International System of Units, Appendix B — conversion factors (ft·lbf 1.355818 N·m; in·lbf 1.129848×10⁻¹ N·m)
- Exact definitions: 1 kgf·m = 9.80665 N·m; 1 kgf·cm = 0.0980665 N·m (standard gravity g₀ = 9.80665 m/s²)
- Displayed to 6 significant digits; conversions computed in full double precision
Frequently Asked Questions
How do I convert Nm to ft-lbs?
Divide newton-meters by 1.355818 (or multiply by 0.737562). So 100 N·m ≈ 73.76 ft·lb and 150 N·m ≈ 110.6 ft·lb. Going the other way, multiply ft·lb by 1.355818 to get N·m — a handy mental shortcut is "N·m is about a third bigger than ft·lb."
What is the difference between ft-lb and in-lb, and why does it matter?
Only the lever arm: 1 ft·lb = 12 in·lb exactly, because both use the same pound-force. It matters because small-fastener specs (electronics, valve covers, aviation hardware) are usually written in in·lb, and reading 89 in·lb as 89 ft·lb over-torques the joint twelve-fold — one of the most common ways threads get stripped. When a spec seems far too high for the fastener size, check the unit before the wrench.
Is torque the same thing as energy, since both are newton-meters?
Dimensionally they match (force × distance), but they are different quantities: torque is force times a PERPENDICULAR lever arm (a vector moment), while energy is force times distance ALONG the motion. That is why torque is written N·m and energy gets its own name, the joule, and why this tool and the energy converter are separate — converting a torque to "joules" would be a category error.
What is kgf·m and where does it appear?
Kilogram-force meter: the torque of one kilogram-force (the weight of 1 kg under standard gravity, 9.80665 N exactly) on a one-meter arm, so 1 kgf·m = 9.80665 N·m. It appears in older metric datasheets, Japanese motorcycle and car service manuals (often as kgf·cm for small fasteners), and Russian-sphere equipment documentation. Many "kg·m" figures in old manuals are kgf·m with the f dropped.
Does converting torque units change how accurate my torque wrench needs to be?
No — conversion is exact to machine precision and adds no error. What matters is rounding the SETTING: 100 ft·lb is 135.582 N·m, and setting a metric wrench to 135 N·m introduces just 0.4%, well inside a typical ±4% wrench tolerance (ISO 6789 Type II). Convert first, round the setting last, and never round the spec before converting.