Percentage Calculator

1. Choose the section that matches your question. Each of the four calculations works independently.
2. Enter both values in the section. Use a comma or period for decimals.
3. Your result appears below the fields right away.

The formulas behind each calculation

Three common pitfalls

• Increasing and then decreasing by the same percentage doesn't get you back to the starting amount. $100 increased by 50% becomes $150; after a 50% decrease, it becomes $75.
• Removing a markup isn't the same as subtracting the same percentage. If $110 already includes a 10% markup, the original amount is 110 ÷ 1.10 = $100, not 110 − 10% = $99.
• Percentages and percentage points are different. If a rate goes from 10% to 12%, it increased by 2 percentage points, but by 20% relative to its previous value.

Quick mental math

10% is the amount with the decimal point moved one place to the left (10% of 350 = 35). From there, 5% is half of 10%, 20% is double, and 15% is 10% + 5%. For tips, interest, or commission with less straightforward amounts, use the calculator to avoid rounding during the calculation. For stacked discounts, such as 20% + 10%, the discount calculator shows the actual total discount.