Four common percentage modes — what is X% of Y, ratio, growth rate, and reverse.
Pick a mode at the top and enter values — the result updates live. Mode 1 (A × B%): 15% of 80 = 12. Mode 2 (B ÷ A × 100%): 12 is 15% of 80. Mode 3 (growth): from 80 to 96 → +20%. Mode 4 (reverse): if 12 equals 15% of X, then X = 80. Negative numbers are allowed; percentages above 100% or below 0% are valid.