Rule of thumb“拇指规则”实际所表达的意思是经验法则。一般来说，这些法则是凭经验所得来的的方法，并不要求完全精确。请注意，这个表达一般都以单数形式出现，a rule of thumb 或者 the rule of thumb。

例句

As a rule of thumb, we need a cup of flower, a cup of sugar and a cup of butter to make a basic sponge cake.

一般来说，做一个基本的海绵蛋糕，我们需要一杯面粉，一杯白糖和一杯黄油。

You should keep your receipts as a rule of thumb.

通常来说，你应该保留发票。

The rule of thumb is to wash your whites and colours separately.

根据经验，白色衣服和其它颜色的衣服应该分开来洗。