When should I use increase vs decrease?
Increase adds the percentage to the base value, while decrease subtracts it from the base value.
Finance
Percentage Calculator
Find what X% of a number is, or see how a value changes when you add or subtract a percentage.
Live calculator output
Enter a base value and percentage to see the result panel update.
How it works
The calculation depends on the mode you choose. For "What is X% of Y?", the formula is: Result = Base Value × (Percentage ÷ 100). For example, 15% of 250 equals 250 × 0.15 = 37.50.
"Increase" adds that result to the base value, while "Decrease" subtracts it. These are the same operations used in retail pricing, tax calculations, and financial analysis. The calculator handles decimals and large numbers with full precision.
Practical example
Suppose you want to find 15% of 250.
The calculator multiplies 250 × 0.15 = 37.50. If you choose "Increase 250 by 15%", the result is 250 + 37.50 = 287.50. If you choose "Decrease 250 by 15%", the result is 250 − 37.50 = 212.50.
This is useful when calculating tips, discounts, or markups on any amount.
Frequently asked questions
Can I enter decimal percentages like 12.5?
Yes. Decimal percentages are supported, so values like 12.5% are calculated correctly.
Why is the result different from my mental math?
Most differences come from rounding. The underlying percentage formula is standard.
How do I reverse-calculate the original price from a discounted price?
Divide the discounted price by (1 − discount/100). For example, if you paid 85 after a 15% discount, the original was 85 / 0.85 = 100.
Is percentage the same as percentage points?
No. A move from 10% to 15% is a 5 percentage-point increase but a 50% relative increase. This calculator works with relative percentages.
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