How do I calculate what percentage X is of Y?

Divide X by Y, then multiply by 100. Formula: (X ÷ Y) × 100 = percentage. Example: 15 is what percent of 60? (15 ÷ 60) × 100 = 25%. So 15 is 25% of 60.

How do I calculate a percentage increase?

Subtract the old value from the new value, divide by the old value, and multiply by 100. Formula: ((New − Old) ÷ Old) × 100. Example: price went from $50 to $65. ((65 − 50) ÷ 50) × 100 = 30% increase.

20% of 150 = (20 ÷ 100) × 150 = 0.20 × 150 = 30. Quick mental math: 10% of 150 is 15, so 20% is 15 × 2 = 30.

How do I find the original price before a percentage discount?

Divide the sale price by (1 − discount rate). Formula: Original price = Sale price ÷ (1 − discount%). Example: an item is $68 after a 15% discount. Original price = $68 ÷ (1 − 0.15) = $68 ÷ 0.85 = $80.

What is the difference between percentage and percentage points?

A percentage point is an absolute difference between two percentages. If your savings rate goes from 10% to 15%, it went up 5 percentage points but increased by 50% (5/10 × 100). This distinction is critical in finance and statistics — media reports sometimes confuse the two.

How do I calculate percentage off a price?

Multiply the original price by the discount percentage divided by 100, then subtract from the original price. Formula: Final price = Original × (1 − discount%). Example: 30% off $200 = $200 × (1 − 0.30) = $200 × 0.70 = $140. You save $60.

Percentage Calculator

Mathematics

Calculate percentage, percentage change, and percentage of total

Mode

Part

Whole

Percentages are everywhere — from tax rates and discounts to test scores, nutrition labels, and financial returns. Yet even people who are comfortable with numbers often reach for their phones when they need to find 17.5% of $84.99 or calculate whether a salary went up 12% from last year.

Our percentage calculator handles every common percentage problem in one place. It solves four types of questions: What is X% of Y? What percent is X of Y? What is the percentage change from X to Y? And what was the original value before a percentage change? Select the calculation type, enter your numbers, and get the answer instantly — with the full formula shown so you can understand the math, not just the result.

From retail discounts and sales tax to investment returns and scientific data analysis, this tool covers every everyday percentage calculation.

Why Percentage Calculator Matters

Percentage literacy is one of the most practically useful math skills. A University of Michigan study found that adults who understand percentages make significantly better financial decisions — including retirement savings, debt management, and investment choices. The applications are endless:

Shopping: Is 30% off a $120 jacket better than $40 off? (Answer: 30% off = $36 savings, so yes.) Understanding discount math helps you evaluate deals accurately.

Finance: A credit card interest rate of 24.99% compounded daily charges more than you expect. A 7% annual return in your 401(k) doubles your money every ~10 years. Percentages drive every personal finance decision.

Health and nutrition: Food labels express nutrients as a percentage of daily values. Understanding what "20% of your daily sodium" actually means in grams helps you make informed dietary choices.

Work and performance: Pay raises, sales commissions, performance metrics, and KPIs are all expressed as percentages. Calculating a 4.5% raise on a $58,000 salary should be instant.

The Percentage Calculator Formula, Explained

P% of Y = (P/100) × Y | X is what % of Y = (X/Y) × 100 | % change = ((New−Old)/Old) × 100

There are four core percentage formulas, each solving a different type of problem:

1. "What is X% of Y?" — Multiply Y by X/100. Example: 15% of $80 = (15/100) × 80 = $12.

2. "X is what percent of Y?" — Divide X by Y and multiply by 100. Example: 12 is what % of 80? = (12/80) × 100 = 15%.

3. "Percentage change from X to Y" — Subtract old from new, divide by old, multiply by 100. Example: price went from $80 to $92: (92–80)/80 × 100 = 15% increase.

4. "What was the original value before a X% change?" — Divide the current value by (1 + X/100). Example: price is now $92 after a 15% increase: 92 / 1.15 = $80 original.

Our calculator solves all four automatically — just select which type of problem you have.

How to Use the Percentage Calculator: Step by Step

Select your calculation type
Choose from the four options: find a percentage of a number, find what percent one number is of another, calculate percentage change, or find the original value before a percent change.
Enter your values
Input the known numbers. The calculator labels each field clearly based on the type you selected, so there's no confusion about which number goes where.
Read your result
The answer appears instantly with the formula applied. For percentage change calculations, positive results indicate an increase and negative results indicate a decrease.
Use the formula view
Expand the "Show formula" section to see exactly how the calculation works — useful if you need to replicate it in a spreadsheet or explain it to someone else.

Percentage Calculator Examples: Real-World Scenarios

Shopping Discount — 35% Off a Sale Item

A laptop is listed at $849.99 and the store is offering 35% off for Black Friday. What is the sale price?

Original price:$849.99

Discount:35%

Calculation

Discount amount: (35/100) × 849.99 = $297.50 | Sale price: 849.99 – 297.50

Result

Sale price: $552.49. You save $297.50. (Also: 849.99 × 0.65 = $552.49 — shortcut for calculating 65% of the original price.)

Salary Increase — What Your Raise Is Worth

Your salary was $65,000. You received a 4.8% raise. What is your new salary and how much extra per month?

Current salary:$65,000

Raise percentage:4.8%

Calculation

Raise amount: (4.8/100) × 65,000 = $3,120 | New salary: 65,000 + 3,120 = $68,120 | Monthly increase: 3,120 / 12

Result

New annual salary: $68,120. Monthly increase: $260 gross (before tax). Your take-home increase will be approximately $178–$205/month depending on your tax bracket.

Test Score — What Percentage Did You Get?

You answered 43 out of 52 questions correctly on a biology exam. What is your score as a percentage?

Correct answers:43

Total questions:52

Calculation

(43 / 52) × 100

Result

Score: 82.69% — a B grade by most standards. You can also use this to find out how many correct answers you need to score 90%: 0.90 × 52 = 46.8, so you needed at least 47 correct.

Common Mistakes to Avoid

Calculating percentage of wrong base — "25% more" means 125% of the original, not 25% of something else. Always identify what your base number is.
Confusing percentage points with percent change — if interest rates go from 4% to 5%, that is a 1 percentage point increase, but a 25% relative increase. These are very different things.
Reversing percentage changes — a 50% drop followed by a 50% gain does not return to the original. $100 → -50% → $50 → +50% → $75, not $100. Percentages are multiplicative.
Not including tax in discount calculations — 35% off a $100 item is $65 before tax. If sales tax is 8%, the final price is $65 × 1.08 = $70.20, not $65.

Tips & Tricks

Quick percentage trick: 10% of any number is just the number divided by 10 (move the decimal left one place). 5% is half of that. 15% is 10% + 5%.
For restaurant tips: 20% = double the 10% figure. On a $47 bill: 10% = $4.70, so 20% tip = $9.40.
For percentage change: if something doubles, that's a 100% increase. If it triples, that's a 200% increase. "100% more" is not the same as "100% of."

Percentage calculations underpin everything from your grocery budget to your retirement plan. Our free percentage calculator handles all four types of percentage problems instantly, with the formula displayed so you always understand the underlying math. For more advanced percentage applications in finance, see our related calculators below.

Percentage Calculator — Frequently Asked Questions

Related Calculators

Percentage Change Calculator

calculate percentage increase or decrease

Discount Calculator

find the final price after any discount

Sales Tax Calculator

add sales tax to any purchase

Tip Calculator

calculate tips by percentage

Profit Margin Calculator

find your business profit margin percentage

Authoritative References

National Council of Teachers of Mathematics

nctm.org — Math education standards reference

Khan Academy — Percentages Course

khanacademy.org — Free percentage learning resource

External links open in a new tab. OmniCalc.us is not affiliated with these organisations.

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