rule of thumb - Robuta Search

https://www.thebalancemoney.com/the-50-30-20-rule-of-thumb-453922

The 50/30/20 rule is a way to allocate money among wants, needs, and savings. Learn its history, how it works, and how to apply it to your finances.

https://laughingsquid.com/?s=rule+of+thumb

https://www.sciencenews.org/archive/physics-rule-thumb-gets-thumbs-down