Year-over-Year (YoY) Growth Calculator (monthly & year-to-date)

Understanding the year-over-year (YoY) growth calculator — concept and principle

This calculator compares this year's monthly figures with the same months last year. It gives year-to-date growth, the latest month against the same month a year ago, the totals and change in value, how many months beat last year and, if you entered all twelve months of last year, last year's full total. Business owners, marketers and analysts use it for monthly and quarterly reporting.

Same months, two years — with the default inputs: +12.4%.

How it is calculated

Year-to-date (YTD) this year = sum of the months entered for this year
Same months last year = sum of the same number of months from last year
YTD growth = (YTD this year − same months last year) ÷ same months last year × 100
Latest month growth = (this year's last month − same month last year) ÷ same month last year × 100
Months above last year = count of months where this year is higher

Enter months in order from January (or the start of your year).

The principle

Many businesses are seasonal: December retail sales or summer travel bookings would distort a month-over-month comparison. Comparing each period with the same period a year earlier removes those normal seasonal swings, so the growth figure reflects real change. Year-to-date totals compare equal numbers of months, which is fairer than comparing a partial year with a full one. The latest month shows recent momentum; the YTD figure shows the trend so far.

Worked example

Defaults: ten months this year from 118,000 to 152,400; twelve months last year from 102,000 to 168,900.

YTD this year = 1,353,500; same 10 months last year = 1,204,000.
Change = 149,500; YTD growth = 149,500 ÷ 1,204,000 = 12.4%.
Latest month: (152,400 − 133,800) ÷ 133,800 = 13.9%.
Months above last year: 10 of 10 compared.
Full last year = 1,514,400.

How to read the result

Latest-month growth above YTD growth, as here, suggests momentum is improving. Every month beat last year, which points to a broad trend rather than one strong month. If inflation was significant, compare growth with the price level to judge real growth. The full last-year total gives a rough reference for this year's outcome if growth continues.

Common mistakes

Comparing a partial year with a full year.
Entering months in a different order for the two years.
Ignoring calendar effects such as an extra trading day or a moved holiday.
Reading nominal growth as real growth during high inflation.

Keep in mind: Year-over-year growth describes what happened. It is not a forecast, and one-off events last year can make this year look better or worse.

Frequently asked questions

What is the difference between YoY and MoM growth?

Year-over-year compares with the same period a year ago, removing seasonality; month-over-month compares with the previous month.

What does year-to-date mean?

The total from the start of the year up to the latest month entered.

Can I use quarterly data?

Yes; enter each quarter as one value in both lists.

Sources: Year-on-year percentage change between the same months of consecutive years, with year-to-date totals over equal numbers of months

Checked 9 Nov 2026. Percentage change (new − old) ÷ old × 100 between the same months of consecutive years (year-on-year comparison); year-to-date totals compare equal numbers of months (arithmetic).

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