Calculate Percentage Change Between Two Values

Excel & Google Sheets

How it works

Percentage change is always (new minus old) divided by old. The subtraction gives the raw change, and dividing by the starting value expresses that change relative to where you began — which is what makes it a percentage rather than just a difference. The formula returns a decimal like 0.15, so format the cell as a percentage to display 15%. Increases come out positive and decreases negative, so the sign tells the story at a glance. The one hard edge: when the old value is zero, the division fails with #DIV/0!, because growth from nothing is mathematically undefined.

B2-A2

The raw change: new value minus old value.

/A2

Divides by the old value, turning the change into a proportion of the start.

Format as %

The result is a decimal (0.15). Apply percentage formatting to show 15%.

When to use it

Use this for month-over-month sales, year-over-year budgets, price changes, and any before/after comparison where "how much did it move, relatively?" matters.

Common mistakes

• ✕#DIV/0! appears when the old value is zero.

  ✓Guard the division: =IF(A2=0,"",(B2-A2)/A2) shows a blank instead. Don't substitute 100% — growth from zero is undefined, not 100%.

• ✕The result shows 0.15 instead of 15%.

  ✓The formula returns a decimal. Format the cell as a percentage (Format → Number → Percent) rather than multiplying by 100 in the formula.

• ✕Old and new values are swapped.

  ✓=(A2-B2)/B2 measures the change backwards and flips the sign. Always subtract the old value from the new one, then divide by the old.