The minimum raise sizing available is identical to the size of the previous raise. This rule is slightly easier to conceptualise using a postflop scenario.
Calculating a pot-sized raise is especially important for playing poker variants with pot-limit betting structures.
Re-raising is not always a legal option in poker, even if we have chips behind.
Must be equal to previous raise size (not necessarily previous bet size).
Pretend we make the call and then look at the total pot. This is the raise amount.
Only if we have faced at least one full sized raise since we bet.