Percentage Calculator
Calculate percentages, percentage change, or find the original value.
· CalcFlow Editorial
Results shown are estimates for informational purposes only. Nothing on CalcFlow is financial, tax, legal, or medical advice. Always consult a qualified professional before making important decisions.
What is a Percentage? A percentage calculator solves three core problems: finding what percent one number is of another, calculating a percentage of a given value, and computing percent change between two numbers. It uses the formula: Percentage = (Part / Whole) x 100.
Rule of Thumb
Quick mental math shortcut: to find 10% of any number, move the decimal one place left. To find 15%, calculate 10% then add half of it. To find 25%, divide by 4. For percent change, always divide by the original (starting) value, not the new one.
Example Calculation
Store discount: original price $80, sale price $68. Percent change = (68 - 80) / 80 x 100 = -15%. The item is 15% off. To verify: 15% of $80 = $12; $80 - $12 = $68.
Key Facts
- •Percentage errors are among the most common math mistakes in consumer finance, tax filing, and investment returns (FINRA Investor Education, 2023).
- •A 1% difference in APR on a $300,000 mortgage equals approximately $170/month or $61,000 over a 30-year term.
- •Percentage change calculations are the basis for inflation rate, GDP growth rate, and stock return reporting.
- •The word "percent" comes from Latin per centum, meaning "per hundred" — percentages are always expressed out of 100.
How to Use
- Select the type of calculation (tab above).
- Enter the two values.
- Click Calculate for the result.
- Switch tabs for different percentage operations.
Formula
Percentage = (Part / Whole) x 100 | Percent Change = (New - Old) / |Old| x 100