Percentage Calculator
Calculate percentage value, increase/decrease, and percent change instantly.
About this tool
Percentages show up everywhere: discounts, tax rates, exam scores, growth metrics, tips. Doing the math in your head is error-prone. The Percentage Calculator handles all three fundamental percentage operations in one tool.
How the Percentage Calculator works
The Percentage Calculator performs three operations: (1) find P% of X, (2) find what percent X is of Y, and (3) find the percentage change from X to Y. It also handles reverse percentage calculations to find original amounts before a discount or markup.
How to use this tool
- Enter your base value in the first field.
- Enter the percentage value in the second field.
- Optionally enter a new value in the third field to compute percentage change.
- Click 'Calculate' to see all computed results.
Common use cases
Calculating a discount amount: what is 30% off a ₹2,500 item?
Finding what percentage a test score represents: 42 out of 50 = ?
Measuring growth: revenue went from ₹50,000 to ₹62,000 — what is the increase?
Reverse calculation: after a 20% discount, the price is ₹800 — what was the original?
Examples
- 20% of ₹1,200 = ₹240. The new value after a 20% increase from ₹1,200 is ₹1,440.
- Revenue change from ₹50,000 to ₹62,000 = +24% growth. The percentage of ₹50,000 that ₹62,000 represents is 124%.
Tips & best practices
- For reverse percentage (finding the original before a discount): divide the discounted price by (1 − discount%), not by (1 + discount%).
- A 20% increase followed by a 20% decrease does NOT return to the original. Starting from 100: +20% → 120, then −20% → 96. Net change: −4%.
- Use the percentage change formula correctly: divide by the OLD value, not the new value. (New − Old) / Old × 100.
Common mistakes to avoid
❌ Dividing by the new value instead of the old value when computing percentage change — this is the most common error.
❌ Adding and subtracting percentages as if they cancel out — they compound, not cancel.
❌ Confusing 'percentage of' with 'percentage change' — 150 is 150% of 100, but it's a 50% increase from 100.
Frequently Asked Questions
Can I calculate percent change between two values?
Yes. Enter the original value as the base and the new value in the third field — the tool computes percentage increase or decrease.
How do I find what percent X is of Y?
Enter X as the base value and Y as the new value. The tool computes what percentage X represents of Y.
Does it handle negative percent change?
Yes. If the new value is less than the original, the result shows a negative percentage representing a decrease.
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