Drift Velocity Calculator

Kaava

How this is calculated

Drift velocity is the net average velocity at which free charge carriers (usually electrons) move through a conductor under an applied electric field. Although individual electrons move rapidly and randomly, their net drift superimposed on this motion is surprisingly slow — often fractions of a millimetre per second. The calculator divides the current I (amperes) by the product of the carrier density n (carriers per cubic metre), the cross-sectional area A (square metres) and the carrier charge q (coulombs).

The relation comes from I = n × A × q × vd, which expresses that current equals the charge per carrier times the number of carriers passing a cross-section per second. Rearranging gives vd = I / (n × A × q). By default q is set to the elementary charge, 1.602 × 10⁻¹⁹ C, appropriate for electrons; you can override it for ions or multiply-charged carriers. The tool also reports the current density J = I / A for reference.

Assumptions: a uniform conductor, a single dominant carrier type and steady-state current. All inputs must use SI units. If n, A or q is zero the denominator vanishes and drift velocity is undefined, so the calculator returns no result in that case. A negative current simply indicates the opposite drift direction; the meter shows the speed magnitude.