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What is X% of Y?
e.g. What is 15% of 200?
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X is what % of Y?
e.g. 30 is what % of 150?
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% Change
Increase or decrease from A to B
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% Difference
Difference between two values
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Increase by %
Add X% to a number
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Decrease by %
Subtract X% from a number
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Percentage Table
Common percentages of your number :
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Types of Percentage Calculations
Also searched as: percentage calculator free | what percent of calculator | percent increase calculator | percentage difference calculator
What is X% of Y — the most basic: multiply Y by X/100. "What is 15% of 80?" = 80 × 0.15 = 12.
Percentage change — how much something changed relative to its starting value. Formula: (New − Old) ÷ Old × 100. A positive result is an increase, negative is a decrease. Used for price changes, growth rates, and score comparisons.
Percentage difference — unlike percentage change, this is symmetric. It uses the average of both values as the base: |A − B| ÷ ((A + B) / 2) × 100. Used when neither value is the "original" — comparing two measurements or prices from different sources.
Use the Percentage Calculator above — enter your values and get instant results. This free online tool calculates how to calculate percentage without any download or signup required. Results update in real time as you type.
Use the Percentage Calculator above — enter your values and get instant results. This free online tool calculates what is 20% of 80 without any download or signup required. Results update in real time as you type.
Percentage change is directional — it measures change from one specific starting value. If a stock goes from $100 to $120, it's a +20% change. Percentage difference is symmetric — used when comparing two values where neither is the "baseline." The same $100 vs $120 gives a 18.2% difference (using the average $110 as the base).
To find the original value before a percentage was added or removed: Original = Result ÷ (1 + Pct/100) for additions, or Result ÷ (1 − Pct/100) for subtractions. Example: if a price of $90 is after a 10% discount, the original was $90 ÷ 0.90 = $100.
No. The second discount applies to the already-reduced price. On a $100 item: 50% off → $50, then 50% off $50 → $25. Total discount is 75%, not 100%. This is why stacked discounts never simply add up — each applies sequentially to a smaller base.