The SI unit of momentum is kilogram metre per second, written as \text{kg·m/s}.

Basic idea

Momentum p is defined as the product of mass and velocity, p=mv.

Since mass has SI unit kilogram (kg) and velocity has SI unit metre per second (m/s), multiplying them gives kg·m/s as the standard SI unit of momentum.

Alternate but equivalent unit

Momentum can also be expressed in newton second (N·s), because 1\\text{N·s}=1\\text{kg·m/s}.

In school-level physics questions, kg·m/s is typically preferred as the SI unit, with N·s mentioned when relating momentum to impulse.