Compound interest calculator
Calculate compound interest: final value, interest earned and capital growth. Free calculator with monthly, quarterly and yearly compounding.
Current for 2026Methodology →
Percentage calculator
Enter a number and a percentage — the calculator returns the result, the value increased and the value decreased by that percentage.
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How we calculate
Result = number × percent / 100. Increased = number + result. Decreased = number − result.
Example: 15% of 200
15% of 200 = 30. Value increased by 15% = 230. Value decreased by 15% = 170.
Frequently asked questions
How do I calculate a percentage of a number?
Formula: result = number × percent / 100. E.g. 15% of 200 = 200 × 15 / 100 = 30.
How do I find what percentage one number is of another?
Formula: percent = (part / whole) × 100. E.g. 30 out of 200 is 30/200 × 100 = 15%.
How do I calculate a percentage increase?
New value = old × (1 + percent/100). E.g. 200 + 15% = 200 × 1.15 = 230.
How do I calculate a percentage decrease?
New value = old × (1 − percent/100). E.g. 200 − 15% = 200 × 0.85 = 170.
What is the difference between a 100% increase and doubling?
A 100% increase means doubling; a 2× increase is the same thing.
How do I calculate percentage change?
Change % = ((new − old) / old) × 100. E.g. 200 to 230: (30/200) × 100 = 15%.
Does the calculator work with fractional percentages?
Yes, you can enter e.g. 12.5%. The calculator handles decimal values.
How do I calculate a discount?
Price after discount = price × (1 − discount/100). E.g. PLN 200 with 15% off = 200 × 0.85 = PLN 170.
How do I reverse a percentage — find the original?
Original = result / (percent/100). E.g. if 30 is 15%, original = 30/0.15 = 200.
Are the results accurate?
Yes, it is exact math rounded to 2 decimal places. The result is accurate for the values entered.
Results are rounded to 2 decimal places and are for informational purposes.