How to calculate year-over-year growth in Excel

The YoY formula

Put months down column A and one year per column. Then this year / last year - 1 is the growth for that month. =(C11-B11)/B11 gives exactly the same answer and reads more like the definition: the change divided by where you started.

Format the cell as a percentage (Home > Number > %, or Ctrl+Shift+%). Don't multiply by 100, or Excel shows 1216%.

Compare a month with the same month a year earlier, not with last month. October against September mixes growth with seasons. This shop's December is always its best month, so a drop in January isn't news.

A YoY column that handles blanks and a zero base

Copy the plain formula down and two rows break. January 2025 is 0 (the shop opened in February), so January gives #DIV/0!. Growth from zero has no meaningful percentage, so show nothing, or "new". November and December 2026 haven't happened yet, so they'd show -100%, which looks like a disaster.

The formula in column D checks both: if last year is 0 or this year is still blank, it returns an empty string. Use "n/a" instead of "" if you'd rather see a label.

If last year was negative (a loss turning into a smaller loss), the plain formula gets the sign backwards: going from -500 to -200 gives -60%. Divide by ABS(last year) to get +60%, or just report the change in dollars, which nobody misreads.

Year-to-date growth: compare the same months

For YTD, add up this year so far and the same months last year. The trap is comparing 10 months of 2026 with 12 months of 2025: =SUM(C2:C13)/SUM(B2:B13)-1 says -12.7%.

=SUMIFS(B2:B13,C2:C13,"<>") only adds last year's months that have a value this year, so both sides cover January to October. That gives 18.5%. But it's still flattered: January 2026 ($3,880) is compared with a January 2025 of $0.

For a like-for-like YTD, use only months that have both years. The formula below adds this year's sales where last year was above 0, and last year's where this year isn't blank: February to October, $46,740 vs $42,720, or 9.4%. That's the honest number.

Same month last year from a dated sales list

If your data is a list of dated sales instead of a monthly table, let SUMIFS build both months from one start date. EDATE(J2,-12) is the same day 12 months earlier (Oct 1, 2025), and EDATE(J2,-11) is the start of the month after it. Using "<" the next month start includes every time of day on the last day.

October 2026 adds up to $1,725 and October 2025 to $1,445, so YoY is 19.4%. Change J2 to any month start and both halves move together. For fiscal years that don't start in January, the same pattern works with a fiscal year start in J2 and EDATE(J2,12) as the end.

Rates: percentage points vs percent

When the thing you're comparing is already a percentage (margin, conversion rate, churn), say which change you mean. A margin going from 32% to 35% is up 3 percentage points, =J4-J3. It's also up 9.4% relative to where it was, =J4/J3-1.

Both are correct, and they're easy to confuse in a report. "Margin grew 3 points" is the clear one. If you write "margin grew 9.4%", someone will read it as 41.4%.