What is X% of Y?
X is what % of Y?
Percentage Change
📊 How the Percentage Calculator Works
This tool solves three common percentage problems using fundamental ratio arithmetic — all explained below.
① X% of Y = (X / 100) × Y
② X is what % of Y = (X / Y) × 100
③ % Change (A→B) = ((B − A) / |A|) × 100
①
What is X% of Y? Multiply Y by the decimal equivalent of the percentage. E.g. 20% of 500 = 0.20 × 500 = 100.
②
X is what % of Y? Divide X by Y then scale to 100. E.g. 30 out of 150 = (30/150) × 100 = 20%.
③
Percentage Change. Measures growth or decline. E.g. price rose from $80 to $100 → ((100−80)/80)×100 = +25%.
Quick Tip: A negative percentage change signals a decrease. The absolute value of the original is used so the formula works for negative starting values too.
All calculations are instant and run entirely in your browser.