“估计”的意思是根据已经知道的情况来大概判断一件事。

The meaning of "估计" is to roughly judge something based on what is already known.

我们说话的时候常用它来表示自己的猜想，比如“我估计他今天不来”。

We often use it in speech to express our guess, for example, "我估计他今天不来" (I estimate he won't come today).