对数平均是一个二个非负数字的数学函数，等于两者的差除以其对数的差。其符号为：

其中都是正整数。

对数平均的计算适用在有关热传及质传的工程问题上。

二个数字的对数平均小于其算术平均，大于几何平均，若二个数字相等，对数平均会等于算数平均及几何平均。

In mathematics, the logarithmic mean is a function of two non-negative numbers which is equal to their difference divided by the logarithm of their quotient. In symbols:

for the positive numbers . This calculation is applicable in engineering problems involving heat and mass transfer.