Less known optimisation: have a slide rule handy[1]. They are amazing for working with proportions which happens all the time in the kitchen.

Just today I needed 200 g of chocolate for a dessert. The bars were 160 g each and made into 21 rectangles. Set the slide rule to 200:160 and read out the value of x:21, which turns out to be 26.25 -- the number of rectangles needed. So convenient to be able to do that quickly and with messy hands.

[1]: https://entropicthoughts.com/kitchen-slide-rule