How to Calculate Percentages
A percentage is just a way of expressing a number as a fraction of 100. The word itself comes from the Latin per centum — "out of one hundred." Once you understand the three core formulas, you can solve almost any percentage problem without a calculator.
The 3 Formulas You Actually Need
1. What is X% of Y?
Multiply Y by X and divide by 100.
Example: What is 20% of 80? → 80 × 20 ÷ 100 = 16
2. X is what % of Y?
Divide X by Y and multiply by 100.
Example: 5 is what % of 20? → 5 ÷ 20 × 100 = 25%
3. Percentage increase or decrease
Subtract the old value from the new, divide by the old value, multiply by 100.
Example: price goes from $40 to $50 → (50 − 40) ÷ 40 × 100 = +25%
Our three calculators above handle each of these formulas instantly. Just enter your numbers, hit Calculate, and the result appears — no steps required.
Popular Calculators
Beyond the basics, we cover percentage problems across finance, marketing, construction, health, and more. A few of the most-used tools:
- Discount Calculator — find the final price after any % off
- Percent Change Calculator — measure growth or decline between two values
- Sales Tax Calculator — add tax by rate or US state
- ROI Calculator — calculate return on any investment
- Markup & Margin Calculator — set your selling price and understand your profit
- Body Fat Calculator — estimate body fat % using the Navy method
About This Site
PercentagesCalculators.com is a free collection of 80+ calculators built for one purpose: fast, accurate answers without sign-ups, ads that block the page, or paywalls. Every tool works on any device, loads in under a second, and shows you the math so you understand the result — not just the number.
Frequently Asked Questions
Q: How do I calculate a percentage without a calculator?
Use the formula: Part ÷ Whole × 100. For example, 12 out of 50 is 12 ÷ 50 × 100 = 24%. For quick mental math, try converting the percentage to a simple fraction first — 25% = ¼, 10% = move the decimal one place left.
Q: What's the difference between percentage and percentage points?
Percentage points measure the absolute difference between two percentages. If your conversion rate goes from 4% to 6%, that's a 2 percentage point increase — but a 50% relative increase. Both are correct; they just describe different things.
Q: Can a percentage be over 100%?
Yes. A percentage over 100% means the part exceeds the whole — which is common when measuring growth. If revenue doubles, that's a 100% increase. If it triples, that's a 200% increase.
Q: How do I reverse a percentage (find the original number)?
Divide the result by the percentage (as a decimal). If a sale price is $80 after a 20% discount, the original price was $80 ÷ 0.80 = $100. Use our Discount Calculator to do this in one step.
Q: Are all the calculators free?
Yes — every tool on this site is completely free. No account, no subscription, no limit on how many times you can use them.