Percentage Change Calculator
Find the percent increase or decrease between two values.
How percentage change works
Percentage change measures how much a value has grown or shrunk relative to its starting point, expressed as a percentage. It is different from a plain percentage of a value — it always compares two numbers.
Enter the original (starting) value and the new (ending) value. The calculator returns the signed percentage change, the absolute change, and whether it is an increase, a decrease, or no change.
The percentage is relative to the original value, so the same absolute change produces a different percentage depending on where you started — a $10 rise from $50 is a 20% increase, but the same $10 rise from $200 is only 5%.
The formula
% change = (New − Original) ÷ |Original| × 100
Subtract the original value from the new value, divide by the absolute value of the original, then multiply by 100. A positive result is an increase; a negative result is a decrease.
Worked example
From 50 to 75
(75 − 50) ÷ 50 × 100 = 50%. The value increased by 50%.
Frequently asked questions
Why can't the original value be zero?
Percentage change is measured relative to the starting value. From zero, any increase is mathematically an infinite percentage change, so the calculation is undefined and rejected.
How is this different from the plain Percentage Calculator?
The Percentage Calculator answers "what is P% of N" or "P is what % of N" for a single value. This tool always compares two values — a before and an after.
What does a negative original value mean here?
The formula divides by the absolute value of the original so the percentage direction still matches the real-world change — for example, a loss narrowing from −$50 to −$25 is correctly reported as a 50% improvement, not a confusing sign flip.
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