Percentage calculator
Solve six common percentage problems in one tool. Find percentages, increases, decreases, and percent changes instantly — no formulas needed.
What is the Percentage Calculator?
Percentages are everywhere — tips at a restaurant, discounts in a store, grades on an exam, a raise at work, inflation in the news. This calculator handles all of those cases from a single interface. Instead of choosing a mode from a menu, you type your question as a sentence and the tool reshapes itself to answer it. It handles six different question types: finding a percentage of a number, finding what percent one number is of another, working backwards from a percentage to the original, and calculating increases, decreases, and percent changes between two values.
Six ways to calculate a percentage
Every percentage problem boils down to one of these six question shapes. Pick the one that matches what you're trying to solve.
What is X% of Y?
Find a percentage of a number. Example: what is 15% of 80? Answer: 12. Formula: (X ÷ 100) × Y. Use this for tips, taxes, discounts, and any time you need to take a fraction of a total.
X is what % of Y?
Find what percent one number is of another. Example: 45 is what percent of 180? Answer: 25%. Formula: (X ÷ Y) × 100. Use this for grades, completion rates, and proportions.
X is Y% of what?
Find the original number when you know a percentage of it. Example: 30 is 25% of what? Answer: 120. Formula: X ÷ (Y ÷ 100). Use this when a sale price is given and you want the original.
X increased by Y%
Add a percentage to a number. Example: 100 increased by 25% is 125. Useful for markups, raises, and inflation adjustments. Formula: X × (1 + Y ÷ 100).
X decreased by Y%
Subtract a percentage from a number. Example: 100 decreased by 25% is 75. Useful for discounts, sale prices, and depreciation. Formula: X × (1 − Y ÷ 100).
Percent change from X to Y
Calculate the increase or decrease between two values as a percentage. Example: from 80 to 100 is a 25% increase. Formula: ((Y − X) ÷ X) × 100. Use this for comparing prices, salaries, or any before-and-after values.
How to think about percentages
A percentage is a fraction with 100 as the denominator. "25%" means 25 out of 100, or 0.25. All six question shapes on this page are variations of the same underlying math: multiplying or dividing by 100 in different combinations. "What is 15% of 80" is 15/100 × 80. "45 is what % of 180" is 45/180 × 100. Once you see that every percentage problem is a proportion — part, whole, and rate — the six shapes become interchangeable views of the same relationship.
Common Uses
- Tip calculation at restaurants: Calculate a 15%, 18%, or 20% tip on the bill total and split it evenly across the group.
- Discount and sale price: Calculate the final price after a 20%, 30%, or 50% discount to decide whether a sale item is genuinely good value.
- Tax and VAT calculation: Add or remove a percentage-based tax to determine the total payable or pre-tax base price of goods and services.
- Grade and score conversion: Convert raw test scores to percentages to compare performance against class averages or admission thresholds.
- Investment return calculation: Calculate the percentage gain or loss on an investment from purchase price to current value.
- Commission and bonus tracking: Sales professionals calculate commission earned as a percentage of revenue to verify payslip accuracy.
- Nutritional label reading: Calculate what percentage of your daily recommended intake a single serving contributes for any given nutrient.
- Percentage change analysis: Calculate month-over-month or year-over-year change percentages for business metrics, expenses, or performance KPIs.
FAQ
How do I find what percentage one number is of another?
Select the "X is what % of Y?" mode, enter both numbers, and the percentage appears instantly. For example: 30 is what % of 200? → 15%.
How do I calculate percentage increase or decrease?
Use the "Percentage Change" mode, enter the original and new values, and the calculator shows the change with a sign (+ for increase, − for decrease).
Can I find X% of a number directly?
Yes. Select the "X% of Y" mode, enter the percentage and the base number. For example: 15% of 200 = 30.
Does the percentage calculator store my data?
No. All calculations run entirely in your browser. Your numbers are never sent to a server or stored after you close the page.
Can I calculate compound percentage growth?
Use the percentage increase mode repeatedly for each period, or switch to the Compound Interest Calculator for multi-period compound growth calculations.
By the Numbers
- The average U.S. restaurant tip is 19.1% of the pre-tax bill (Toast Restaurant Trends Report, 2024)
- U.S. state sales tax ranges from 0% (Oregon, Montana, New Hampshire) to 7.25% base rate (California)
- Global average inflation was 5.7% in 2023, down from a peak of 8.7% in 2022 (World Bank)
- A 10% increase followed by a 10% decrease (or vice versa) results in a net 1% loss — a common mathematical misconception