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Percentage Change Calculator

Enter an initial value (v1) and a final value (v2). We compute ((v2 − v1) / v1) × 100 as a percentage using math.js BigNumber and the shared RapidRatio number pipeline.

Calculate

Starting amount—the denominator of the percent change (enter as text, e.g. 0.1).
Updated amount you are comparing to v1 (e.g. 0.2 gives a 100% increase).

Result

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Enter values and press Calculate.

How to calculate percentage change

Percent change answers: “How much did a value move, relative to where it started?” Use the same units for both inputs (dollars with dollars, meters with meters, plain counts with counts).

  • Record the initial value (v1)—the baseline before the change. This becomes the bottom of the fraction, so it must not be zero.
  • Record the final value (v2)—the amount after the change.
  • Apply the formula ((v2 − v1) / v1) × 100. Positive results are increases; negative results are decreases. Press Calculate here to have RapidRatio format the result for display.

Units, rounding, and limits

The calculator is unitless and does not model taxes, compounding, or business rules. Displayed numbers are capped at 14 decimal places for presentation, then trailing zeros are trimmed. For values such as 0.1 and 0.2, arithmetic stays in BigNumber space end to end so you do not inherit binary floating-point noise from JavaScript’s default number type.

FAQ

How do I calculate a percentage increase?

Subtract your starting value from the new value, divide by the starting value, then multiply by 100. That is ((final − initial) / initial) × 100. A positive answer is a percentage increase; a negative answer is a decrease.

Why does the calculator show an error when the initial value is zero?

Percent change divides by the initial value. When that value is zero, the ratio is undefined, so the tool reports Division by Zero instead of a misleading number.

Are small decimals like 0.1 and 0.2 accurate?

Yes. Inputs are parsed as strings into math.js BigNumber values, and the result is formatted with controlled precision—avoiding the floating-point rounding noise you get from plain JavaScript numbers.

Disclaimer. RapidRatio is informational only. It is not financial, tax, business, or professional advice. Verify results and assumptions with qualified professionals before making decisions.