Direct answer
Percentage change compares a new value with an original value. Percentage difference compares two values symmetrically when neither one is the baseline.
What this calculation tells you
These calculations describe relative size rather than only the numerical gap between two values. Percentage change preserves direction and answers how far a later or revised value moved from its baseline. Percentage difference removes that direction and describes how far apart two peer measurements are relative to their typical magnitude.
The choice of reference changes the meaning of the result. Before calculating, decide whether one value is genuinely the starting point or whether both observations should have equal status.
Where it is used
Business and retail
Track changes in sales, prices, costs, conversion rates, inventory levels, or customer demand between periods.
Finance and economics
Describe movements in balances, earnings, market values, inflation measures, output, or employment when a prior period is the baseline.
Science and quality control
Compare experimental measurements, instrument readings, production samples, or observed values when neither reading is automatically the reference.
Public reporting
Communicate changes in population, energy use, emissions, participation, or service performance while keeping the comparison period explicit.
Common situations
- Checking whether a new supplier price increased relative to the previous quotation.
- Comparing two laboratory measurements taken by equally valid methods.
- Explaining why a rate moved from one period to the next without confusing percent with percentage points.
- Reviewing a sequence of increases and decreases whose reference value changes after every period.
The reference value is the key
For percentage change, subtract the original value from the new value, divide by the absolute value of the original, then multiply by 100. Using the original magnitude keeps a positive result for an increase and a negative result for a decrease, including when the baseline itself is negative.
For percentage difference, take the absolute difference and divide by the average of the two values' absolute magnitudes. Swapping the values does not change the answer. With two zero values, the raw ratio has a zero reference magnitude; the linked calculator intentionally reports 0% for that identical-value case rather than presenting an undefined comparison.
Worked example
A price moving from 80 to 100 has a change of 20. Relative to the original 80, the percentage change is 20 ÷ 80 × 100 = 25%.
If 80 and 100 are two independent measurements, their percentage difference is 20 ÷ 90 × 100, or about 22.22%.
Common mistakes
Dividing by the new value reverses the intended baseline. Dividing by a signed negative baseline can also reverse the direction: under this convention, −80 to −100 is a decrease of 25%, not an increase. Using the average denominator for a before-and-after comparison changes the question. Reporting a percentage change from zero is undefined.
- Name the baseline before calculating.
- Use the original magnitude in the denominator.
- Use an absolute difference only for a symmetric comparison.
Why equal percentages do not cancel
An increase and a decrease with the same percentage act on different baselines. If a value rises by 20%, the new value is larger; a later 20% decrease is taken from that larger amount, so it finishes below where it started.
This matters when reading prices, investment performance, defect rates, population figures, and any report that chains changes across periods. The order of the changes may not affect the final multiplication, but describing them as a net zero movement is still wrong.
- Keep the baseline for every period visible.
- Do not add successive percentage changes when the reference value moves.
- Use percentage points when comparing two rates measured on the same scale.
Practical questions
Frequently asked questions
Should I use percentage change or percentage difference?
Use percentage change when one value is the original, previous, planned, or reference value. Use percentage difference when the two values are peers and swapping their order should not change the result.
Can percentage change be greater than 100%?
Yes. An increase can exceed the entire magnitude of the original value. A value rising from 40 to 100, for example, has increased by more than its original amount.
Is a change from 20% to 25% a 5% increase?
It is an increase of 5 percentage points. Relative to the original 20% rate, it is a 25% percentage increase. State which measure you mean.