What this calculator does
Month-over-month growth compares consecutive months, which makes it the most immediate read on momentum available: it reacts to a single good or bad month faster than any longer-window measure can.
That immediacy is also the catch. A single month is noisy, and a rate that looks spectacular or alarming often means very little once annualised: which is exactly why this calculator shows the annualised equivalent alongside the raw monthly figure, so the two questions “what happened last month” and “is this a trend” stay separate.
The formula
The monthly rate is the plain percentage change between the two months. Annualising it asks a different question: if this exact monthly rate repeated for twelve months running, compounding on itself each time, what would the yearly total be? That is (1 + monthly rate)^12 − 1, and it grows far faster than the monthly figure alone suggests, because each month compounds on the last.
| Term | Meaning |
|---|---|
| This month | The current month’s figure. |
| Last month | The immediately preceding month’s figure. |
| MoM growth | (This month − last month) ÷ last month × 100. |
| Annualised rate | What the MoM rate compounds to over twelve months, equal to (1 + MoM)^12 − 1. |
The inputs explained
| Field | What to enter |
|---|---|
| This month’s value | This month’s figure. |
| Last month’s value | Last month’s figure, the immediately preceding month. |
When to use it
Tracking early-stage momentum
A new product or a young company changes too fast for annual comparisons to be useful yet. MoM is the natural cadence for something that might double in a quarter.
Catching a problem quickly
A sudden negative MoM figure is a much earlier warning sign than waiting for the YoY comparison to turn, since YoY only reacts once a full year of history has rolled past the bad month.
Sanity-checking a growth pitch
A claim like “we are growing 15% a month” sounds impressive until it is annualised: this calculator shows the extraordinary annual rate that implies, which is a fast way to tell an outlier month from a sustainable pattern.
Setting a monthly target that adds up over a year
Working backwards from a desired annual growth rate to the monthly rate needed to get there is the same calculation run in reverse: a steady 5% a month compounds to a very large annual number.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How a fixed prior month reads across different outcomes
A steady base of 10,000 last month against a range of results this month.
| This month | MoM growth | Change | If sustained, annualised rate |
|---|---|---|---|
| 9,800 | -2.00% | -200.000 | -21.5% |
| 10,000 | 0.000% | 0 | 0.000% |
| 10,200 | 2.00% | 200.000 | 26.8% |
| 10,500 | 5.00% | 500.000 | 79.6% |
| 11,000 | 10.0% | 1,000.00 | 213.8% |
| 12,000 | 20.0% | 2,000.00 | 791.6% |
How the same result reads against different starting points
The current month held at 10,600 while the prior month it is compared against varies.
| Last month | MoM growth | Change | If sustained, annualised rate |
|---|---|---|---|
| 8,000 | 32.5% | 2,600.00 | 2,828.1% |
| 9,000 | 17.8% | 1,600.00 | 612.5% |
| 9,600 | 10.4% | 1,000.00 | 228.4% |
| 10,000 | 6.00% | 600.000 | 101.2% |
| 10,600 | 0.000% | 0 | 0.000% |
| 12,000 | -11.7% | -1,400.00 | -77.4% |
Questions
Why does a small MoM rate turn into such a large annual figure?
Because it compounds. A 5% monthly gain does not add up to 60% a year (5 × 12): it compounds to 79.6%, since each month’s growth applies to a base that already includes every prior month’s growth.
Is MoM growth reliable for judging a whole year?
Not on its own. A single month can be unusually strong or weak for reasons that have nothing to do with the underlying trend: a launch, a holiday, a one-off event. MoM is best read as a series over several months, not a single data point.
What does a negative annualised rate mean?
That the monthly decline, if it continued for twelve months, would shrink the figure toward zero rather than below it: an annualised rate can approach −100% but mathematically never reach or pass it, since each month only ever multiplies the remaining value.
How is MoM different from YoY?
MoM compares consecutive months and reacts fastest to recent change but carries the most noise from seasonality. YoY compares the same month a year apart and is slower to react but cancels out seasonal patterns within the year.
Should I use this for a metric that resets each month, like a sales target?
No: MoM growth assumes both figures measure the same cumulative or point-in-time quantity. Comparing two independent monthly totals works; comparing a running total to a monthly reset does not.
For a comparison that cancels out seasonality, see the year-over-year growth calculator. For quarterly reporting, use the quarter-over-quarter growth calculator.