Calculate a percentage increase or decrease
Enter an original value and a new value to see the difference and the percentage change. This is useful for checking a price change, supplier cost movement, sales comparison, or target adjustment.
How percentage change works
Subtract the original value from the new value to find the change. Divide that change by the original value, then multiply by 100. For example, a cost moving from 80 to 100 changes by 20, which is a 25% increase.
Interpret price changes in context
A percentage change does not explain why a price moved or whether a new selling price is profitable. Review supplier cost, discounting, operating expenses, and tax basis before updating a product. Use the profit margin calculator and product records to review the practical effect.
Measure increases and decreases without losing the starting point
Percentage change compares a new value with its original value. The original value is the denominator, so direction matters: moving from 80 to 100 is a 25% increase, while moving from 100 back to 80 is a 20% decrease. These are not contradictory because the starting values differ.
Percentage change formula
Percentage change = (new value − original value) ÷ original value × 100. A positive result is an increase, a negative result is a decrease, and zero means the two entered values are equal.
Worked percentage-change examples
Supplier cost increase
An item cost moving from 240 to 276 changes by 36. Dividing 36 by the original 240 gives 0.15, so the supplier cost increased by 15%. That does not mean the selling price or profit margin also changed by 15%.
Retail price decrease
A selling price moving from 500 to 425 changes by −75. Dividing −75 by 500 gives −0.15, so the price decreased by 15%. Check the actual discounted price with the profit-margin calculator before interpreting the commercial effect.
Sales comparison
If recorded sales value moves from 20,000 to 23,000 on the same reporting basis, the increase is 15%. Before drawing a conclusion, verify dates, stores, returns, discounts, stockouts and transaction status through the relevant sales report.
Why an original value of zero is different
Ordinary percentage change is undefined when the original value is zero because division by zero is not possible. Report the absolute movement and relevant context instead of describing it as an infinite percentage increase. When both values are zero, there is no numerical movement, but the standard percentage-change formula remains undefined.
Percentage change is not percentage points
If a margin moves from 20% to 25%, it increases by 5 percentage points. Relative percentage change is (25 − 20) ÷ 20 × 100, which equals 25%. State which measure you mean so readers do not confuse a five-point movement with a 5% relative change.
A large percentage can come from a small starting value
Moving from 1 unit to 3 units is a 200% increase, but the absolute change is only 2 units. Review both the numeric difference and the percentage. Small bases, short periods and unusual events can make a percentage look more important than the underlying activity.
Use comparable values and periods
- Use the same currency, unit and tax basis.
- Compare equivalent stores, products or categories.
- Use matching date and time boundaries.
- Handle returns, cancellations and missing records consistently.
- Note promotions, closures, stockouts or one-time purchases.
- Do not treat correlation as proof of the cause.
Connect the calculation with business records
Confirm price changes in product records, trace supplier-cost changes through purchase records, and compare sales on a consistent basis in Sales Reports. Use the sales-report review checklist before acting on an unusual result.
This calculator checks the relationship between two entered numbers. It does not forecast demand, explain a change, calculate inflation, determine profitability or replace accounting and statistical analysis.