Month-over-Month (MoM) Calculator

MoM is the percentage change of a value in the current month compared with the previous month. The formula is: (this month's value - last month's value) / last month's value x 100%. Example: January revenue of $100,000 and February revenue of $110,000 gives MoM = (110 - 100) / 100 x 100% = +10%. A positive value means growth, a negative value means decline, and 0% means flat. MoM is useful for reading the pace of short-term change, for example MRR growth, sales, or active users.

MoM compares this month with last month, while YoY (year-over-year) compares this month with the same month last year. MoM is sensitive to short-term and seasonal swings: for example, a +30% MoM jump in December sales from November may just be a holiday-season effect. YoY neutralizes seasonal effects, making it better for reading annual trends. The two complement each other: use MoM for the monthly pulse, YoY for the yearly direction.

Annualization projects a monthly rate into an annual equivalent with compounding: (1 + m)^12 - 1, where m is the monthly rate in decimal form. Example: an average MoM of 10% per month equals (1.10)^12 - 1 = 213.84% per year, far above 10% x 12 = 120%, because each month grows on an already larger base. This approach is valid when the monthly rate is relatively stable and repeatable, for example SaaS MRR growth. It is not valid for one-off spikes, base effects, or data that swings up and down randomly, because the result would be misleading.

Negative MoM means the value fell compared with last month. Example: 80 dropping to 60 means MoM of -25%, so this month's value is only 75% of last month's. Negative MoM is not a verdict: a -5% dip after a +40% rise the month before can be a normal correction. Also remember the recovery asymmetry: after a 50% drop, you need a 100% gain to get back to the starting point.

The base effect happens when a percentage looks dramatic only because the starting number is small. Example: users rising from 10 to 100 is recorded as +900%, even though the absolute gain is only 90 users. MoM is best read in pairs: percent for speed, absolute numbers for scale. Be wary of claims of hundreds of percent growth from a tiny base.

The percent change calculator computes the generic percentage change between two numbers without monthly framing, series, or annualization. The annualized rate of return calculator computes CAGR from investment dates and values. The holding period return calculator computes the return of a single holding period including its income. This calculator is MoM-specific: MoM from two values with worked steps, a monthly series table with average MoM and trend, annualization (1+m)^12 - 1 plus its naive version, a target value solver, and a two-series comparator. See also: <a href="/tools/percent-change-calculator/">Percent Change Calculator</a>, <a href="/tools/annualized-rate-of-return/">Annualized Rate of Return Calculator</a>, <a href="/tools/holding-period-return/">Holding Period Return Calculator</a>.

A SaaS startup with $200,000 MRR growing +10% MoM for 6 months reaches $200,000 x 1.10^6 = $354,312. Retail stores use MoM to read post-promo sales, product teams use MoM of active users, and finance teams use negative MoM on churn because falling churn is good news. For a steadier trend, use the average MoM over 3-6 months, not a single month.