What is the difference between torque and horsepower?

Torque is rotational force. Power is the rate at which work is done. They measure different things, and the relationship between them is fixed and simple.

Torque is a twisting force, measured in newton metres (Nm) or pound-feet. It is what the engine applies to turn the crankshaft — the shove.

Power is torque multiplied by rotational speed. In practical terms:

Power = torque × revs (with a constant depending on units).

This is the whole relationship, and everything else follows from it. An engine producing high torque at low revs can produce the same power as one producing lower torque at high revs.

What each does in practice:

Torque determines how hard the car pulls at a given moment, and how it feels. High torque at low revs gives effortless acceleration without changing down, which is why diesels and electric cars feel responsive in normal driving.

Power determines what the car can ultimately do — top speed, and acceleration when you are prepared to use the revs. A high-revving engine with modest torque can be very fast, because it multiplies moderate torque by a large number of revolutions.

The gearbox complicates the intuition, and this is what most explanations miss. Gearing multiplies torque. A low gear multiplies engine torque enormously at the wheels while reducing speed. So the torque at the crankshaft matters far less than people assume — what matters at the wheels is power, because gearing can trade torque for speed but cannot create power.

This is why, for outright acceleration, power is the more meaningful figure, and why a small high-revving engine with the right gearing can outperform a torquey one.

Why electric cars feel so quick. Electric motors produce peak torque from zero rpm, with no need to build revs and often no gearbox — so full shove is available instantly.

The old line — torque is how far you take the wall, power is how fast — captures the feel rather than the physics.