Calculadora de Mudança Relativa
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
r = |b − a| / |a| × 100
About this calculator
The Relative Change Calculator determines the percentage change between two values using the formula |b − a| / |a| × 100. It measures how much the final value (b) differs from the initial value (a) relative to the initial, expressing the result as a percentage. By using absolute values, the calculator always returns a positive value, indicating the magnitude of change regardless of increase or decrease.
This tool is especially useful for comparing quantities on different scales, such as price variations, economic indices, or scientific measurements. For example, a $10 increase on a $100 item (10%) differs from a $10 increase on a $1000 item (1%). Relative change allows fair comparison by normalizing the variation by the initial value.
To use the calculator, enter the initial value (a) and the final value (b) in the corresponding fields. The result is displayed as a percentage, representing the relative change between the two numbers. Ensure both values are numeric and the initial value is non-zero, as division by zero is undefined.
Cautions: Make sure the initial value (a) is not zero, because the formula requires division by a. Also, relative change does not indicate direction (increase or decrease) due to the absolute value; to know whether there was an increase or decrease, check if b is greater or less than a. This calculator is ideal for analyses where percentage magnitude matters more than sign.
Frequently asked questions
What does relative change mean?
Relative change is the percentage change between two values, calculated as |b − a| / |a| × 100. It shows how much the final value changed relative to the initial, in percentage terms.
Can I use the calculator if the initial value is zero?
No, because the formula divides by the initial value. If a is zero, the division is undefined. In that case, relative change cannot be calculated.
Does the calculator show whether there was an increase or decrease?
No, because it uses absolute value. The result is always positive. To know the direction, compare b with a: if b > a, there was an increase; if b < a, a decrease.
What is the difference between relative change and absolute change?
Absolute change is the simple difference (b − a), while relative change is that difference divided by the initial value, as a percentage. Relative change allows comparing variations on different scales.
Can this calculator be used for percentage increase or discount?
Yes, but note that the result is always positive. For a discount, the final value is smaller than the initial; the percentage result indicates the magnitude of the reduction.