Percentage Calculator
Quickly calculate percentages, percentage changes and what percent one number is of another.
Educational estimate only. This is not financial, investment, tax, legal or lending advice, a quote or a guarantee. Read the disclaimer.
Your inputs
How this calculator works
A zero denominator makes the corresponding ratio undefined, shown as not applicable. The A% of B result is a number, not a currency amount. Negative values are allowed; percentage changes from a negative baseline can be counterintuitive and should be interpreted alongside the original values. Results are rounded to two decimal places.
Dollar results are in USD and generally rounded to the nearest whole dollar; salary equivalents and percentage outputs use two decimal places. Calculations retain JavaScript floating-point precision between steps rather than rounding every payment to cents. Displayed components may not sum exactly to displayed totals. Payoff times use whole monthly payment periods. Defaults are examples, not current rates or recommendations.
Full methodology · About the publisher and corrections
Content and calculation checks: October 12, 2026. Educational estimates; no independent professional certification is claimed.
Worked example: 25 and 100
With A = 25 and B = 100, A is 25% of B. Twenty-five percent of 100 is 25. The change from 25 to 100 is 300%.
Percentage change can become unintuitive when the starting value is zero or negative, so interpret the original numbers alongside the percentage.
Practical guide
Three common percentage questions
- “What percent is A of B?” Divide A by B, then multiply by 100.
- “What is A% of B?” Multiply B by A/100.
- “How much did this change?” Divide the difference by the starting value, then multiply by 100.
For investment returns over time, use the ROI Calculator rather than a simple percentage-change result.
How to use the result
Change one assumption at a time to compare scenarios. For example, test a lower rate, larger contribution, different term or extra payment. This makes the calculator most useful as a decision-support tool rather than a single-number answer.
Important financial decisions can depend on taxes, fees, eligibility rules, lender policies, market returns and personal circumstances that this simplified calculator does not capture.
Frequently asked questions
Is this percentage calculator free?
Yes. SumStride calculators are free to use and do not require an account.
Are the results exact?
No. Results are estimates based on the values you enter and the assumptions described on this page. Real-world fees, taxes, rates, policies and timing can differ.
Does SumStride save my inputs?
No account is required. The calculator runs in your browser; SumStride does not need your entered values to perform the calculation.