Short answer: to convert newton meters to foot-pounds, multiply by 0.7376. To go the other way, multiply foot-pounds by 1.355818. Those come from NIST's own SI conversion tables, which give 1 pound-force foot = 1.355 818 newton meters. So 100 Nm is about 74 ft-lb, and 100 ft-lb is about 136 Nm. For practical garage work, rounding to 0.74 and 1.36 is close enough — the error is well inside any wrench's published tolerance.
The conversions you actually meet
| Newton meters | Foot-pounds | Typically | |
|---|---|---|---|
| 5 Nm | 3.7 ft-lb | Small covers, sensors | Needs an in-lb or Nm wrench |
| 10 Nm | 7.4 ft-lb | Valve covers, trim | Needs an in-lb or Nm wrench |
| 25 Nm | 18.4 ft-lb | Brake caliper hardware | 3/8 in wrench |
| 45 Nm | 33.2 ft-lb | Caliper brackets, drain plugs | 3/8 in wrench |
| 110 Nm | 81.1 ft-lb | Passenger-car wheel nuts | 1/2 in wrench |
| 120 Nm | 88.5 ft-lb | Passenger-car wheel nuts | 1/2 in wrench |
| 140 Nm | 103.3 ft-lb | Larger wheels, light trucks | 1/2 in wrench |
| 200 Nm | 147.5 ft-lb | Truck wheels, hub nuts | 1/2 in wrench |
The third and fourth columns are there because the conversion is rarely the real question. What people actually want to know is whether the wrench they own can be set to the number in front of them, and that depends on which drive size they are holding. What size torque wrench do I need maps ranges to jobs.
The dual-scale reading error
Here is the mistake that matters, and it has nothing to do with arithmetic. Most click wrenches sold in the US print two scales: foot-pounds on one side of the handle and newton meters on the other, or one above the other on the same barrel. The EPAuto wrench's manual, for example, states its range as both 10-150 ft-lb and 13.6-203.5 Nm — the same wrench, the same mechanism, two printed rows.
Set 120 on the Nm scale when you meant 120 ft-lb and you have tightened a wheel to 89 ft-lb instead of 120 — low, but survivable. Set 120 on the ft-lb scale when the spec was 120 Nm and you have applied 163 Nm, which is 36% over, and that is how studs stretch and rotors distort. The second error is far more likely, because the ft-lb scale is usually the prominent one on a US-market wrench.
The short version
- Decide which unit your spec is in before you touch the wrench, not during.
- Say the unit out loud when you set the handle. It sounds silly and it works.
- Check the direction of the error: if the Nm number is bigger than the ft-lb number for the same job, you are reading the right rows.
- Nm figures are always numerically larger than the ft-lb equivalent. A spec of 120 that you think is Nm but is actually ft-lb is a 36% over-torque.
- If your car's data is metric and you do this often, buy a wrench whose primary scale matches — or a digital one that switches.
- Never set a click wrench between its marked graduations and hope. Round to the nearest marked value.
Which cars publish which unit
Nearly every manufacturer now publishes torque in newton meters, including the US domestic makers, because vehicle engineering is metric worldwide. What varies is the owner's handbook: a US-market handbook usually gives the wheel-nut figure in foot-pounds for the driver, while the workshop service data behind it is in Nm. So the unit you meet depends on which document you are reading rather than which badge is on the car.
Two places this bites. Online forum figures are quoted in whatever the poster had, frequently without a unit at all. And bicycle, motorcycle and carbon-component specs are metric-only — there is no foot-pound convention in those categories, which is why a dedicated Nm wrench exists for them. Best torque wrenches for bikes covers that end.
Why the conversion is not quite the end of it
Having converted a figure, you still have to set it on a scale that may not have a mark where your number lands. A micrometer click wrench adjusts in fixed graduations — 1 ft-lb on the EPAuto, 5 ft-lb on the Precision Instruments split-beam, 1 in-lb on the TEKTON 1/4 in — and a converted metric figure almost never falls neatly on one.
Convert 110 Nm and you get 81.1 ft-lb. On a wrench with 1 ft-lb graduations you set 81 and the 0.1 is irrelevant, because it is a tenth of a percent and the wrench is certified to several percent at best. On a wrench with 5 ft-lb graduations your choices are 80 or 85, and you take 80 — round down, always, because under-torque on most fasteners is correctable and over-torque frequently is not. What you must not do is try to set the handle between two marks: the mechanism is not designed to resolve that and the resulting figure is not the one printed on it.
A digital wrench removes this entirely by accepting any value in any unit, which is a quieter argument for one than the accuracy spec usually quoted. For click wrenches, the practical rule is to check your wrench's graduation size before you decide whether its scale is fine enough for metric work — click vs digital goes through the trade in full.
The spec that no conversion helps with
Some modern metric specifications are not a single figure at all. A torque-to-yield fastener — common on cylinder heads and some suspension hardware — is specified as a torque followed by an angle: tighten to 40 Nm, then a further 90 degrees. The first number converts; the second does not, because degrees are degrees in both systems and no foot-pound figure substitutes for them.
If you meet a spec like that, the honest answer is that a plain click wrench cannot complete the job. You need an angle gauge or an electronic wrench with an angle mode, and torque-to-yield fasteners are usually single-use and must be replaced rather than re-torqued. It is worth recognizing the format so you stop before you strip something, rather than converting the first half and improvising the second.
The other units you may run into
Two more appear occasionally. kg-m (kilogram-meter) turns up in older Japanese service data; 1 kg-m is about 9.807 Nm, or 7.233 ft-lb. And in-lb (inch-pounds) is the US small-fastener unit: twelve inch-pounds to a foot-pound, so 89 in-lb is 7.4 ft-lb or 10 Nm. The GEARWRENCH 85077 displays all five units, which is the tidiest solution if your sources are mixed. Best inch-pound torque wrenches covers the low-torque tools.
What we would do
Write your car's wheel-nut figure on a strip of tape stuck to the inside of your toolbox lid, in both units, taken from the owner's handbook. That removes the conversion from the moment you are crouched beside a wheel, which is the moment the mistake gets made. If your service data is metric and you work from it often, the GEARWRENCH 85077 switching to Nm is worth the money; otherwise a printed dual scale is fine as long as you read the right row.