1 US customary table spoon (~14.8ml) is conventionally taken as 15ml, a teaspoon as 5ml, a cup as 240ml. That's roughly what you get when you buy a set of measuring spoons/cups as well; some may be a tad smaller (following the US measurements), and some are aligned with these metric values — the difference is mostly negligible.

These are quite standardised unless you are using something like Australian tablespoons¹ (but then any American following that recipe would run into problems as well). The US customary cup and spoon measures were introduced exactly to solve the problem of measurement ambiguity in recipes! Nineteenth century cookbooks can be hard to follow because of the significant variation in the interpretation of smidgens, dashes, pinches, and (then) spoons and cups.

1: Are these really a thing? Any Australian care to chime in?