Percentage Calculator
% of a number, what percent X is of Y, or percentage change.
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About this calculator
Percentages express ratios against 100. The three everyday questions — finding a share, finding a proportion, and measuring change — trip up even professionals because the base always differs.
Percentage change uses the absolute old value as base so that +50% followed by −50% lands at −25%, not zero. That asymmetry surprises many.
Formula
X% of Y = Y × X/100 · What% = X/Y × 100 · Change = (New−Old)/|Old| × 100
How to use the Percentage Calculator
- Pick the question you're answering from the dropdown.
- Fill X and Y per the labels shown.
- Results update as you type — no button needed.
Frequently Asked Questions
Why doesn't +20% then −20% cancel out?
After +20% the base grows to 120. Losing 20% of 120 = −24 → final 96. Percentages chain multiplicatively on shifting bases.
How do I add 18% GST mentally?
Multiply by 1.18 — e.g., ₹500 becomes 500 × 1.18 = ₹590.