How do I quickly calculate percentages?
The five most common percentage questions in one place. Pick a mode, enter two values, get the result and the formula.
Works for shopping (how much off, price after sale), finance (price increase, salary raise), business (margin), schoolwork (homework), and any everyday calculation where people usually just google "percentage calculator".
How to use it
- At the top, pick a mode: one of five percentage operations.
- Enter two values in the fields.
- The result with the formula shows immediately in the green banner.
- "X% of Y" mode: classic "what is X percent of Y". E.g. 20% of 150 = 30.
- "X is what % of Y" mode: the reverse question. E.g. 30 is what % of 150? = 20%.
- "Increase" or "discount" mode: the price after a raise or sale.
- "Change" mode: by what percent does the new value differ from the old.
When this is useful
Seven common scenarios:
- Shopping with a discount. A $200 dress at 30% off costs $140. The "discount" mode shows you the final price.
- Checking if a discount is real. "Promo: $50 off $250", what percent is that really? "X is what % of Y" mode shows 20%.
- Negotiating a raise. "From $5,000 to $5,750, what percent is that?". Change mode answers: +15%. Useful framing in a salary conversation.
- Inflation and price comparison. Bread cost $4, now costs $5.50. What's the percentage increase? Change mode shows +37.5%.
- Store margin. Bought a product for $80, selling at $120. That's a 33% margin. Or for the deeper margin-vs-markup distinction, use our margin and markup calculator.
- Homework problems. "Calculate 80% of 150" → "X% of Y" mode → 120. Kids see the formula and can check their answer.
- Restaurant tip. 15% of an $80 bill = $12 tip. Or use our tip calculator, which also splits the bill across diners.
Questions and answers
Multiply the number by the percent as a decimal. 20% of 150 = 150 × 0.20 = 30. Or divide by 100 and multiply: 150 × 20 / 100 = 30. The "X% of Y" mode does this and shows the formula step by step.