% Percentage Calculator
Four calculation modes for every percentage problem.
20% of 80
How to Use This Calculator
Four tabs cover the four most common percentage problems. Click the tab for your question, enter the numbers, and the answer updates instantly. Each tab also shows the full label so you can confirm you are using the right formula.
Use "X% of Y" when you need to find a part of a whole. Example: what is 15% of 200? Answer: 30.
Use "X is ?% of Y" when you have both numbers and want the percentage. Example: 45 is what percent of 180? Answer: 25%.
Use "% Change" when comparing an old value to a new value. Enter the original first, then the new value. Positive means increase; negative means decrease.
Use "% Difference" when neither value is the reference point β for example, comparing two measured quantities of equal standing.
Percentage Formulas
A percentage is just a ratio expressed out of 100. Percent means "per hundred," so 35% = 35/100 = 0.35. You can always convert between percentages and decimals by dividing or multiplying by 100. This makes percentage problems easy to check: 20% of 50 should equal 0.20 Γ 50 = 10.
Worked Examples
Where This Comes Up in Real Life
Shopping discounts are a direct application of percentage. A Β£120 jacket reduced by 25% costs 120 Γ (1 - 0.25) = Β£90. VAT works in the opposite direction: a Β£100 item with 20% VAT costs 100 Γ 1.20 = Β£120. When you see a price "including VAT" and need the pre-tax price, divide by 1.20: Β£150 including 20% VAT = Β£150 / 1.20 = Β£125 before tax.
Percentage change is central to comparing data over time. If a company's revenue was Β£2.4 million last year and is Β£2.76 million this year, the growth rate is (2.76 - 2.4) / 2.4 Γ 100 = 15%. Investors compare this to inflation and sector averages to decide if the growth is meaningful. Bank interest rates, mortgage APR, and investment returns all use the same percentage change logic with time periods added in.
Frequently Asked Questions
What is 20% of 80?
20% of 80 = 0.20 Γ 80 = 16. The formula is: Percentage Γ Number Γ· 100 = Result.
What percentage is 15 of 60?
15 Γ· 60 Γ 100 = 25%. The formula: (Part Γ· Whole) Γ 100 = Percentage.
How do I calculate percentage increase?
Percentage increase = ((New β Old) Γ· Old) Γ 100. Example: from 50 to 75: ((75β50)Γ·50)Γ100 = 50% increase.
How do I reverse a percentage (find the original)?
If a number after X% increase is Y, the original = Y Γ· (1 + X/100). Example: 132 after 10% increase β original = 132 Γ· 1.10 = 120.
What is the percentage difference?
Percentage difference = |A β B| Γ· ((A + B)/2) Γ 100. It measures relative difference when there's no clear "original" value.