---
tag: 026J1MG2NW
kind: concept
name: Flux through a surface
aliases: [flux-integral]
msc: [26B15]
uses: [0TD904MG06, 065HE5V98E]
sources:
  - url: https://en.wikipedia.org/wiki/Flux
    locator: General mathematical definition (surface integral)
---

## Summary

The flux of a vector field through an [[oriented surface|0TD904MG06]] measures how much of the field passes through the surface. It counts flow in the direction of the chosen normal.
It is the [[surface integral|065HE5V98E]] of the normal component of the field. For a velocity field of a fluid, it is the volume of fluid that crosses the surface per unit time.