How the Month-Over-Month Calculator works
Month-over-month (MoM) analysis answers a simple question: how did a number change from last month to this month, and what does that pace of change imply if it kept going? This calculator uses the standard percent-change formula, then extends it two ways that are common in finance and operations reporting: an annualized rate that compounds the monthly change over a full year, and a forward projection that carries the same monthly rate out for a chosen number of months.
The formula
For a previous month value P and a current month value C, the month-over-month percent change is:
MoM% = (C − P) ÷ P × 100
A positive result means the value grew from the prior month; a negative result means it shrank. Because the formula divides by the previous value, that value must be greater than zero for the percentage to be defined — this calculator will not compute a result if the previous month value is zero or negative.
Annualizing a monthly rate
To translate one month's change into a comparable yearly figure, the calculator compounds the monthly rate (as a decimal, r = MoM% ÷ 100) over 12 periods:
Annualized% = ((1 + r)^12 − 1) × 100
This is a "what if this kept happening every month" figure, not a prediction. A modest 2% monthly gain compounds to roughly 27% over a year, which is why small monthly swings can look dramatic once annualized — useful for comparing metrics on a common yearly basis, but not a guarantee of future performance.
Projecting the trend forward
The calculator also projects the current value forward using the same monthly rate:
Projected value = C × (1 + r)^n
where n is the number of months you choose to project. Like the annualized rate, this assumes the exact same percentage change repeats every month, which real-world metrics rarely do — treat it as a straight-line extrapolation for comparison, not a forecast.
Worked example
Say revenue was $12,000 last month and $12,840 this month. The change is $840, and MoM% = 840 ÷ 12000 × 100 = 7.00%. Compounded over 12 months, that rate would reach an annualized 125.22%. Projected 6 more months at the same 7% monthly rate, the value would grow to roughly $19,269.
Growth metrics versus cost metrics
The math is identical whether you are tracking revenue, active users, expenses, or any other monthly figure. The calculator's "metric type" setting only changes how the result is framed: for a growth metric (revenue, sales, users) an increase is treated as favorable, while for a cost metric (expenses, spending) an increase is treated as unfavorable. Choose whichever framing matches what you are tracking; the underlying calculation does not change.