Free percentage calculator — percent of a number, change, and markup
Four everyday percentage problems solved in one place: find what X% of a number is, express one number as a percentage of another, measure the change between two figures, and add or take off a percentage. Each answer appears with its formula written out underneath, so you can check the working rather than trust a black box.
How to use the percentage calculator
- Choose a Mode: What is X% of Y, X is what % of Y, Percentage change from A to B, or Increase / decrease Y by X%.
- Type the two numbers into the fields — their labels rename themselves to match the mode you picked.
- In the increase or decrease mode, choose the Direction before calculating.
- Click Calculate to see the answer and its formula, then use Copy result.
Everyday uses
- Shopping — sale prices, flat discounts, and restaurant tips.
- Exams and marks — a score as a percentage of the total.
- Business reporting — revenue growth or decline between two periods.
- Pricing — apply a markup, margin, or commission to a base amount.
- Tax and billing — sanity-check a GST or service-charge line before paying.
The formulas behind each mode
Percent of a value is (X / 100) * Y. One number as a percentage of another is (X / Y) * 100. Percentage change from A to B is ((B - A) / A) * 100, which comes out negative when the value has fallen. Increasing or decreasing works out to Y * (1 + X / 100) or Y * (1 - X / 100). Division by zero is blocked, so an impossible input returns a clear message rather than a misleading number.
Runs entirely in your browser
Your numbers are never uploaded — the arithmetic happens locally in JavaScript, with no account and no tracking. Working out a loan instalment instead? Use the EMI calculator, or convert measurements with the unit converter.
Need a custom tool or internal utility built for your team? Get in touch with SR Infobiz.