In short
- One pound-force foot equals 1.355818 newton metres.
- One newton metre equals about 0.737562 pound-force feet.
- Convert the unit before deciding that two published torque figures disagree.
- A matching conversion still needs the same engine, market and test specification.
Torque tables create arguments that disappear as soon as the units match. I keep the source value and unit together, convert with the published factor, and round only the number shown on the finished poster.
What is the difference between Nm and lb-ft?
Nm and lb-ft are different units for the same quantity, torque. One pound-force foot is 1.355818 Nm, while one Nm is about 0.737562 lb-ft.
A larger numerical value in newton metres does not mean the metric source found more torque. It is the same reason a distance has a different number in miles and kilometres. Convert first, then ask whether both sources describe the same car.
How do you convert Nm and lb-ft?
Divide Nm by 1.355818 to calculate lb-ft. Multiply lb-ft by 1.355818 to calculate Nm, and keep the unrounded result until the final display value.
| Newton metres | Pound-force feet | Rounded display |
|---|---|---|
| 100 Nm | 73.7562 lb-ft | 73.8 lb-ft |
| 200 Nm | 147.5124 lb-ft | 147.5 lb-ft |
| 300 Nm | 221.2686 lb-ft | 221.3 lb-ft |
| 451 Nm | 332.6405 lb-ft | 333 lb-ft |
Converting a value that was already rounded can leave a small difference when it is converted back. That is ordinary rounding, not evidence that the engine changed.
What do the torque unit names mean?
A newton metre combines SI force and distance units. A pound-force foot combines one pound-force with one foot of distance. Both express a moment of force around an axis.
NIST lists the imperial quantity as pound-force foot, written lbf ft. Car brochures and dashboards often shorten that to lb-ft or reverse it to ft-lb. I keep the source wording while checking the calculation against the formal conversion factor.
The reversed label can also be used for energy in other contexts. On a car engine specification headed TORQUE, the surrounding label makes the intended quantity clear.
Is torque the same as power?
Torque and power are different quantities. Torque measures turning effect, while power relates work to time, so converting Nm to lb-ft does not convert torque into bhp or kW.
Engine speed connects the two in an engine calculation, but a peak torque figure does not tell you where that peak occurs or how long the engine holds it. That is why one torque number cannot rank two cars for acceleration.
The separate BHP, PS and kW guide deals with power units. The 0 to 60 guide explains why a complete acceleration claim needs the car and test context as well.
How are torque figures handled on the posters?
The poster keeps the signed Nm value and, where supplied, its checked pound-force-foot conversion. The source unit, exact car and rounding decision stay together in the model record.
The Mk4 Supra is a useful check. Its signed 451 Nm converts to 332.6405 lb-ft, and the established poster design shows 333 FT-LB. Both numbers describe the same torque after sensible rounding.
A conversion match is only the first check. The specification checking process also confirms the market, engine and model year before the figure publishes.
What is the source and limit of the conversion?
NIST publishes 1.355818 as the conversion factor from pound-force foot to newton metre. That factor converts the unit accurately, but it cannot confirm that two source figures belong to the same engine or market.
The factor comes from the NIST Guide to the SI conversion table. The examples above use that factor and round only for display.
Browse the reviewed catalogue to see torque beside the exact drawn car. Do not use this arithmetic alone to choose a specification for an unidentified engine.
Questions people actually ask
- How do you convert Nm to lb-ft?
- Divide the newton-metre figure by 1.355818. For example, 300 Nm is about 221.3 lb-ft, which a specification table may round to 221 lb-ft.
- How do you convert lb-ft to Nm?
- Multiply the pound-force-foot figure by 1.355818. A quoted 200 lb-ft converts to about 271.2 Nm before any sensible display rounding is applied.
- Are lb-ft and ft-lb the same on car specifications?
- Car specifications often use both labels for torque. The formal quantity in the NIST conversion table is pound-force foot, written lbf ft, while the poster retains its established FT-LB display label.
- Does more torque always mean a faster car?
- No. A torque figure alone does not determine acceleration. Engine speed, gearing, power, vehicle mass, traction and the test conditions all affect the result, so convert units without turning one number into a complete performance ranking.
Written by Jonathan in Derby. Last updated .