Drift Velocity Calculator

About this calculator

The drift velocity is the average speed at which charge carriers (typically free electrons) move through a conductor due to an electric field, given by vd = I / (n·A·q), where I is the current, n is the charge-carrier density (carriers per unit volume), A is the conductor's cross-sectional area, and q is the charge per carrier. It's usually startlingly slow — often on the order of millimetres per second in a copper wire — because electrons zigzag between collisions with the metal's lattice ions far more than they move net distance.

Electrical engineers and physics students use this calculation to distinguish drift velocity from the much faster signal propagation speed (close to the speed of light) — a light bulb turns on almost instantly not because individual electrons race down the wire, but because the electric field that pushes them propagates near light-speed through the whole circuit. It's also used to size conductors and understand current density limits in wiring design.