Nm to Joules Calculator
Convert newton-metres to joules for work done, and see why torque in Nm is not energy.
150 J in other energy units
| Unit | Value |
|---|---|
| kJ | 0.15 kJ |
| calories | 35.8509 cal |
| kcal | 0.035851 kcal |
| watt-hours | 0.041667 Wh |
| BTU | 0.142173 BTU |
| foot-pounds | 110.6343 ft·lb |
| electronvolts | 9.36226e+20 eV |
The same units, two different quantities
A joule is a newton-metre — one joule is the work done pushing with one newton through one metre:
W = F × d
So converting newton-metres of work to joules is a conversion by a factor of exactly 1. 50 N over 3 m is 150 J.
Torque in Nm is not energy
Here is the trap. Torque is also measured in newton-metres, but it is force × lever arm — a twisting effort, not work done. A wrench held at 40 N·m that never moves does no work at all, and 40 N·m of torque is emphatically not 40 J of energy.
Torque becomes work only when something rotates through an angle:
W = τ × θ, with θ in radians
40 N·m through two full turns is
40 × 4π = 502.7 J — not 80 J. Using degrees, or forgetting
the angle entirely, is the usual mistake.
Why the SI names differ
Both are kg·m²/s² dimensionally, so the units cannot tell them apart. The convention is to write energy in joules and torque in newton-metres, and never to mix the names, precisely so a reader can tell which quantity is meant. It is one of the few places where SI relies on naming discipline rather than dimensions.
The same distinction applies in imperial units: foot-pounds of energy versus pound-feet of torque. Many sources use "ft-lb" for both, so check which is meant.