Percentage Calculator
Solve all three common percentage problems at once — find a percent of a number, what percentage X is of Y, and the percent change between two values. Results update instantly.
How to use this percentage calculator
- 1To find what 20% of 250 is: enter 20 in the Percent field and 250 in the X field — the first result is your answer.
- 2To find what percentage 250 is of 300: enter 250 as X and 300 as Y — the second result shows the ratio.
- 3To find the percent change from 250 to 300: enter 250 as X and 300 as Y — the third result shows the increase or decrease.
- 4For sale price calculations: enter the discount percentage and the original price to see the discount amount, then subtract from the original.
- 5For tip calculations: enter the tip percentage and the bill total as X to instantly see the tip amount.
- 6For salary increase: enter your old salary as X and new salary as Y to see your percentage raise.
How it's calculated
Percent of a number: result = (P ÷ 100) × X. Ratio: X is (X ÷ Y) × 100 percent of Y. Percent change: ((Y − X) ÷ X) × 100, where X is the original value and Y is the new value.
About the Percentage Calculator
Percentages are one of the most practically useful areas of everyday mathematics, yet they are also a surprisingly common source of confusion and errors — in shopping decisions, salary negotiations, investment returns, and test score reporting. Understanding the three core types of percentage problems, and when to use each one, makes you significantly more capable of interpreting numbers in the real world.
The first type is finding a percentage of a number — for example, calculating 15% of a $45 restaurant bill for a tip, or figuring out how much tax you will owe on a purchase. The formula is simple: divide the percentage by 100, then multiply by the number. So 15% of $45 is 0.15 × $45 = $6.75. This is the most common percentage calculation in daily life and the one most people can do mentally with practice.
The second type is the ratio problem: what percentage is one number of another? A student who scores 43 out of 50 on a test wants to know their percentage score — that is 43 ÷ 50 × 100 = 86%. A business owner who sells 340 units out of a target of 400 is at 85% of goal. This type of calculation appears constantly in performance metrics, test scores, and budget tracking. The key thing to remember is that the denominator is always the reference value — the total, the target, or the whole.
The third type — percent change — is where most people make mistakes, because it requires careful attention to which value is the original. Percent change always divides by the starting value, not the ending value. If a stock goes from $80 to $100, the gain is $20, and the percent change is $20 ÷ $80 × 100 = 25% — not 20% (which is $20 ÷ $100). If it then falls back to $80, the percent decrease from $100 is $20 ÷ $100 = 20%. Notice that a 25% gain followed by a 20% loss returns you to the starting point — this asymmetry is important in finance and everyday comparisons.
Mental math shortcuts for percentages can save you significant time. Finding 10% of any number is trivial — just shift the decimal one place to the left ($340 → $34). From there, 5% is half of 10%, 20% is double 10%, and 25% is a quarter of the total. For tip calculations, 20% of $67.50 is $13.50 — far faster to compute as "double 10%, which is 2 × $6.75." These shortcuts work because percentages scale linearly: 3% of a number is exactly three times 1% of that number. Building this intuition eliminates the need for a calculator in most real-world situations.
Frequently asked questions
What is the difference between percent of and percent change?
Percent of finds a portion of a single number — for example, 15% of $60 is $9. Percent change compares two different numbers and expresses the difference as a percentage of the original — if a price goes from $60 to $69, that is a 15% increase. The two calculations look similar but answer completely different questions. Percent change always has a direction (increase or decrease) while percent of simply finds a fraction.
How do I calculate a restaurant tip?
Enter your tip percentage (15, 18, or 20 are common) in the Percent field and your total bill in the X field. The first result is your tip amount. Add that to your bill for the total payment. For a quick mental estimate, 10% of any number is just the number divided by 10 — so 20% is double that, and 15% is 10% plus half of 10%.
How do I find the original price before a discount?
If an item is on sale for $80 after a 20% discount, work backwards: the sale price equals 80% of the original (since 20% was removed). Divide $80 by 0.80 to get the original price of $100. Another way to think about it: enter 80 and 100 as X and Y in the calculator and verify the percent change shows -20%.
What is the difference between percent change and percent difference?
Percent change is directional — it measures how much a value changed from one specific starting point to another. Percent difference is symmetric — it compares two values without treating either as the 'original.' Percent difference uses the average of both values as the denominator, making it useful when neither value is clearly the baseline, such as comparing prices from two different stores.
How do I calculate a percentage increase in my salary?
Enter your current salary as X and your new salary as Y. The percent change result shows your raise percentage. For example, if you go from $52,000 to $56,160, that is an 8% increase. You can also reverse this: if you are told you are getting a 10% raise starting from $52,000, enter 10 as the percent and 52000 as X — the result ($5,200) is the raise amount, and adding it gives $57,200.
Why does 50% off followed by 50% on not return to the original price?
This is a classic percentage trap. If a $100 item is discounted 50%, it drops to $50. Adding 50% of $50 back is only $25, bringing it to $75 — not $100. Percentages are always calculated on the current base value, which changes with each operation. This is why sequential percentage changes cannot simply be added together. To return from $50 to $100 you would need a 100% increase, not 50%.