How Percentage Increase Classic works
Percentage change measures how much a value has grown or shrunk relative to its starting point. Given an original value and a new value, this calculator applies the standard formula % Change = (New − Original) / Original × 100 to tell you exactly how large the shift is, in which direction, and how that translates into an absolute difference and a growth multiplier.
Formula and method
Subtract the original value from the new value to get the absolute change (New − Original). Divide that difference by the original value, then multiply by 100 to express it as a percentage. If the result is positive, the value increased; if it is negative, the value decreased; a result of 0% means no change. The growth multiplier (New ÷ Original) gives the same relationship as a factor — for example, a 25% increase corresponds to a multiplier of 1.25, meaning the new value is 1.25 times the original. Because the formula divides by the original value, that value must be nonzero, or the percentage change is mathematically undefined.
Going the other direction: value from a percentage
If you already know the original value and the percentage increase (or decrease) you want to apply, rearrange the formula to solve for the new value: New = Original × (1 + Percent / 100). For a decrease, use a negative percentage — for example, applying a -10% change to 200 gives 200 × (1 − 0.10) = 180. This calculator's two inputs (original and new value) let you verify that relationship in reverse: enter the original value and the new value you expect, and check that the reported percentage matches the change you intended.
Common sources of error
- Swapping original and new: the order matters — (New − Original) / Original is not the same as (Original − New) / New, and swapping the two will flip the sign and change the magnitude.
- Confusing percentage change with percentage points: going from 20% to 25% is a 5 percentage-point change but a 25% relative increase (5/20 × 100).
- Zero or near-zero original values: percentage change is undefined when the original value is 0, and can look misleadingly huge when the original value is very small.
Applications
Percentage increase and decrease calculations show up constantly: tracking price changes, sales growth, salary raises, population change, discount markups, and test-score improvement. Always report the original and new values alongside the percentage so readers can verify the direction and scale of the change themselves.