How it works
Three formulas cover nearly every percentage question:
X% of Y = (X ÷ 100) × Y
X is what % of Y = (X ÷ Y) × 100
% change = ((New − Old) ÷ |Old|) × 100
X is what % of Y = (X ÷ Y) × 100
% change = ((New − Old) ÷ |Old|) × 100
Frequently asked questions
Percent vs percentage points?
Going from 10% to 15% is a 5 percentage point rise but a 50% percent increase. Politicians mix these up constantly.
How do I reverse a % increase?
A 20% rise then 20% fall doesn't return to start: $100 → $120 → $96. Division, not subtraction, reverses percentages.
Quick mental math trick?
10% = move decimal one left ($250 → $25). Build any percent from 10s, 5s and 1s.
Disclaimer: This calculator provides estimates for educational purposes only and is not financial, tax, or legal advice. Consult a qualified professional before making financial decisions.