曼宁公式（英语：Manning formula）是一个估测液体在开放管道（即明渠流）或非满管流中平均速度的经验公式。开放管道中的液体是因重力而流动。曼宁公式最早是由法国工程师Philippe Gauckler在1867年提出，在1890年爱尔兰工程师罗伯特·曼宁也提出相同的公式。

曼宁公式如下：

其中：

The Manning formula is also known as the Gauckler–Manning formula, or Gauckler–Manning–Strickler formula in Europe. In the United States, in practice, it is very frequently called simply Manning's Equation. The Manning formula is an empirical formula estimating the average velocity of a liquid flowing in a conduit that does not completely enclose the liquid, i.e., open channel flow. All flow in so-called open channels is driven by gravity. It was first presented by the French engineer Philippe Gauckler in 1867, and later re-developed by the Irish engineer Robert Manning in 1890.