Percentages show up constantly in everyday decisions — is that "40% off" sale actually a good deal, what should you tip, did your score improve. A few formulas cover nearly every situation you'll run into.
Finding a Percentage of a Number
Formula: (Percentage ÷ 100) × Number
Example: 15% tip on a bill of 2,000 → (15 ÷ 100) × 2,000 = 300.
Calculating a Discount
Formula: Final Price = Original Price × (1 − Discount% ÷ 100)
Example: an item priced at 5,000 with 30% off → 5,000 × (1 − 0.30) = 3,500.
To find just the amount saved rather than the final price: 5,000 × 0.30 = 1,500 saved.
Percentage Increase or Decrease
Formula: ((New Value − Old Value) ÷ Old Value) × 100
Example: a price rising from 800 to 920 → ((920 − 800) ÷ 800) × 100 = 15% increase. A negative result means a decrease — the formula works both ways.
What Percentage One Number Is of Another
Formula: (Part ÷ Whole) × 100
Example: scoring 42 out of 60 on a test → (42 ÷ 60) × 100 = 70%.
Skip the Manual Math
All four of these work instantly in the Percentage Calculator — pick the calculation type you need and get the answer without re-deriving the formula each time.
A Common Mix-Up Worth Knowing
"25% off" and "reduced by 25 percentage points" are not the same thing when percentages are already involved — e.g., an interest rate dropping from 10% to 8% is a 2 percentage-point drop, but it's actually a 20% decrease in the rate itself ((10−8)/10 × 100 = 20%). Financial news headlines mix these up constantly, so it's worth reading carefully which one is actually being reported.
FAQ
How do I calculate a percentage increase back to the original value?
Divide the new value by (1 + percentage/100) — e.g., a value of 920 after a 15% increase: 920 ÷ 1.15 = 800.
Why does my discount math not match the store's final price?
Check whether tax is applied before or after the discount — some stores apply tax on the discounted price, others on the original, which changes the final total.
Can a percentage be more than 100%?
Yes — for comparisons like percentage increase, values well above 100% are normal (e.g., a value tripling is a 200% increase).