About Percentage Calculator
All four common percentage operations side-by-side — X% of Y, X is what % of Y, percent change between two numbers, percent increase/decrease. Formulas shown alongside results so the math is auditable. Useful for quick math during meetings, finance, shopping, or stats.
The four operations
- X% of Y —
(X/100) × Y. Use for: tip on a bill, discount on a price, sales tax. - X is what % of Y —
(X/Y) × 100. Use for: market share, pass rate, percentile. - Percent change —
((new - old) / old) × 100. Use for: growth, return, rate of change. - Percent increase / decrease —
Y × (1 ± P/100). Use for: applying a raise, applying a discount.
Common workflows
Tip a meal. Bill 67.50, tip 18%: 67.50 × 0.18 = 12.15. Total 79.65.
Year-over-year revenue. Last year 1.2M, this year 1.5M: (1.5 - 1.2) / 1.2 = 25% growth.
Sales tax. 145 × 1.08875 = 157.87 (NYC tax of 8.875%).
Discount finally cheap? Sticker 89.99, 30% off: 89.99 × 0.70 = 62.99.
Performance bonus. Salary 95k, 8% raise: 95000 × 1.08 = 102,600.
Why a tool
The math is one line each, but having all four pinned beats opening a calculator app for 40 seconds of reasoning.
Frequently asked questions
20% of 150?
30. The formula is
(percent / 100) × value.30 is what percent of 150?
20%. Formula:
(part / whole) × 100.From 100 to 125, what percent change?
+25%. Formula:
((new - old) / old) × 100.Discount on 250 by 15%?
Final price 212.50. Formula:
value × (1 - percent/100).Difference between change and difference?
Change is asymmetric — uses old as base. Difference is symmetric — uses average. Percent change is more common in finance and growth metrics.
Compound percent?
Not in this tool. For repeated growth (interest), use the Loan Calculator for compound math.
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Last updated: 2025-01-15