Percentage Formulas
The Core Formulas
| Calculation | Formula | Example |
|---|---|---|
| X% of Y | Y × X ÷ 100 | 15% of 200 = 30 |
| X is what % of Y | X ÷ Y × 100 | 30 is 20% of 150 |
| % Change | (New − Old) ÷ Old × 100 | 50 to 75 = +50% |
| % Difference | |A − B| ÷ ((A + B) ÷ 2) × 100 | Diff between 40 and 60 = 40% |
| Markup % | (Price − Cost) ÷ Cost × 100 | Cost $50, Sell $75 = 50% markup |
| Margin % | (Price − Cost) ÷ Price × 100 | Cost $50, Sell $75 = 33.3% margin |
| Discount | Price × (1 − Discount% ÷ 100) | $80 at 25% off = $60 |
| Sales Tax | Price × (1 + Tax% ÷ 100) | $50 + 8% tax = $54 |
| Tip | Bill × Tip% ÷ 100 | $60 bill, 20% tip = $12 |
Converting Between Forms
| From | To | Method |
|---|---|---|
| Decimal → % | 0.75 → 75% | Multiply by 100 |
| % → Decimal | 42% → 0.42 | Divide by 100 |
| Fraction → % | 3/4 → 75% | Divide, then × 100 |
| % → Fraction | 60% → 3/5 | Put over 100, simplify |
Try these formulas with our calculators: Percentage Calculator · % Change · Markup · Tip · Discount
Helpful context
A formula page is valuable because it gives you a reference point when you know the concept but do not want to reconstruct the algebra from memory. Keeping the base formulas together makes it easier to move between classroom math, spreadsheet work, budgeting, and quick everyday calculations without second-guessing the setup each time.
Practical example
The Percentage Formulas page is also a good double-check when you are moving between calculator results and spreadsheet work. Many people know the rough idea of the math but still make small setup errors when a value needs to be rounded, reformatted, or interpreted in context. Keeping the explanation tied to the specific percentage formulas workflow makes those mistakes easier to catch.
More Percentage Tools
Why Percentages Matter
Percentages are one of the most widely used mathematical concepts in everyday life. From calculating sales tax and tips to understanding interest rates, investment returns, and statistical data, percentage literacy is essential for making informed financial and academic decisions.
In finance: Interest rates, investment returns, inflation, and tax rates are all expressed as percentages. A 1% difference in mortgage interest on a $300,000 loan amounts to roughly $60,000 over 30 years. Understanding percentages helps you make better financial decisions.
In academics: Grades, test scores, and statistical significance are percentage-based. Knowing how to convert between fractions, decimals, and percentages is fundamental to math, science, and data analysis courses.
In business: Profit margins, market share, growth rates, and discount structures all rely on percentage calculations. Being able to quickly calculate and interpret percentages is a core professional skill in virtually every field.
Use our free percentage tools above to handle any calculation quickly and accurately. Whether you need to find what percentage one number is of another, calculate a percentage increase or decrease, or convert between fractions and percentages, we have a tool for it.