Percentage Calculator: Percent Of & Percentage Change

Choose the percentage calculation you need

For “A% of B,” A is the percentage and B is the base amount. For “change from A to B,” A is the starting value and B is the ending value. For “A is what percent of B,” A is the part and B is the total.

A% of B = A ÷ 100 × B.
Percentage change = (B − A) ÷ |A| × 100.
A as a percent of B = A ÷ B × 100.

Examples

15% of 200 is 30. A price changing from 80 to 100 increases by 25%. A part of 30 out of a total of 120 is 25%.

Zero and negative values

Percentage change from zero is undefined, as is division by a zero total. The calculator shows an error for those cases. For negative starting values, percentage change uses the absolute starting value as its denominator; moving from −100 to −50 is shown as a positive 50% change. Check that this convention fits your use case.

Percent versus percentage points

A rate moving from 5% to 6% rises by one percentage point, or 20% relative to its starting rate. These quantities answer different questions. This tool calculates relative percentage change.

About this calculator

Prepared by the UtilitiesWeb team at The Alpha 1 Company. Estimates are educational illustrations, not personalised financial advice, lending decisions, or guaranteed outcomes. Verify important decisions against provider documents and qualified advice where needed.

Methodology updated: 1 November 2026. Example rates and costs are assumptions, not live market quotes. Amounts are calculated at full precision and rounded for display.