Year‑over‑year (YoY) percentage change compares a value in one period to the **same period one year earlier** — for example, this March compared to last March, or Q2 this year compared to Q2 last year. It uses the same percentage change formula as any other comparison, but applied specifically to values that are **one year apart**.

YoY change = (This year’s value − Last year’s value) / Last year’s value × 100

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Why YoY instead of month‑over‑month?

Month‑over‑month comparisons (like March → April) can be misleading for businesses with **seasonal patterns**. A toy store’s April revenue will naturally differ from its December revenue — even if the business is growing — simply because demand changes seasonally. Comparing **March this year to March last year** removes that seasonal noise and reveals the underlying trend. YoY is ideal for: - retail with seasonal peaks - tourism and hospitality - agriculture - quarterly business reporting - any dataset with predictable seasonal cycles

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Worked example: quarterly revenue

A company’s Q2 revenue was $840,000 last year and $945,000 this year. What is the YoY percentage change?

Step 1: Last year’s value = 840,000 This year’s value = 945,000

Step 2: (945,000 − 840,000) / 840,000 × 100 = 105,000 / 840,000 × 100 = 12.5

Step 3: Revenue grew **12.5% year‑over‑year** in Q2.

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A note on comparing percentages

If you compare two YoY growth rates themselves — for example: - 12.5% YoY this quarter - 9% YoY last quarter — the difference between them is measured in **percentage points**, not percent. For a refresher, see percentage points vs percentage change.

Ready to calculate your own YoY numbers? Use the percentage change calculator with last year’s and this year’s values.