Percentage Calculator
Calculate percentages instantly: find X% of a number, what percent one value is of another, or the percentage change between two numbers.
Enter values above to see the result.
Three Percentage Calculations, One Simple Tool
Percentages come up constantly — splitting a restaurant bill, tracking a stock's daily move, calculating a discount at checkout, or figuring out how much your rent went up. Yet most calculators make you remember the formula. This Percentage Calculator gives you three clearly labelled modes so you can get to the answer without thinking about the math.
Mode 1 — What is X% of a number?
Type the percentage and the base number, and the result appears as you type. If you want to know how much a 20% tip is on a £45 meal, enter 20 and 45 — you get £9 instantly, with a plain-English sentence you can copy straight into a message or spreadsheet.
Mode 2 — What percentage is one number of another?
This answers questions like: "I scored 68 out of 80 — what's that as a percentage?" Enter 68 as the Part and 80 as the Total. The tool tells you it's 85%. Useful for test scores, survey results, budget utilisation, and any situation where you have a part and a whole.
Mode 3 — Percentage change between two values
Enter an original value and a new value to see whether it went up or down and by how much. The result is colour-coded: green for an increase, red for a decrease. If your monthly revenue rose from £4,200 to £5,040, the tool shows +20% in green so the direction is impossible to miss.
Common Use Cases
- Retail discounts — "A jacket is 30% off its £120 price. How much do I pay?" (Mode 1: 30% of 120 = £36 off, so £84.)
- Grade and score reporting — Convert raw marks to a percentage for a CV, report card, or exam recap.
- Finance and investing — Track percentage gains and losses on positions without needing a separate spreadsheet.
- Performance metrics — Compare this month's conversion rate (2.4%) to last month's (2.1%) and quickly see a +14.3% improvement.
- Nutrition and diet tracking — Calculate what percentage of daily calories comes from fat, carbs, or protein.
- Salary negotiations — Find out what a proposed pay rise means as a percentage, or work backwards from a target increase.
How Percentage Change Handles Negatives
When the original value is negative (e.g. a loss position), the calculator still works correctly because the formula divides by the absolute value of the starting number. This ensures consistent direction — going from -10 to -5 correctly shows a +50% improvement, not a confusing negative result.
Privacy
Every calculation runs entirely in your browser. No values are sent to any server, nothing is stored, and the tool works offline once the page has loaded. Safe to use with sensitive financial or personal figures.
Frequently Asked Questions
How do I calculate 15% of a number?↓
Switch to the "% of a number" tab, enter 15 in the Percentage field and your number in the Value field. The result appears instantly. For example, 15% of 80 is 12.
How is percentage change calculated?↓
Percentage change = ((New Value − Original Value) / |Original Value|) × 100. A positive result means an increase; a negative result means a decrease. For example, going from 200 to 250 is a +25% change.
What does "X is what percent of Y" mean?↓
This answers questions like "30 is what percent of 120?" — meaning, how large is 30 relative to 120 expressed as a percentage. The formula is (Part / Total) × 100, so 30 out of 120 is 25%.
Can I calculate percentage decrease?↓
Yes — use the "% change" tab. Enter the original (larger) value in the From field and the new (smaller) value in the To field. The result will be a negative percentage, showing how much the value decreased.
Does this calculator store my data?↓
No. All three calculation modes run entirely in your browser with no server calls. Your numbers are never sent anywhere and nothing is logged.