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Compound Monthly Growth Rate Calculator

Get the smooth monthly growth rate behind any change.

How it is calculated

The tool finds the one steady monthly rate that turns the start value into the end value: CMGR = (end ÷ start)1 ÷ months − 1, shown as a percent. It also gives the whole-period change, (end ÷ start − 1) × 100, and the multiple, end ÷ start, written like 2.63x. Start and end are any metric in the same unit (revenue, users, subscribers), and months is the number of monthly steps between them, so January to December of the same year is 11 steps, not 12. Start, end and months must all be above zero, because a zero or negative value has no growth rate. A result below zero means the value shrank each month on average. The rate is a geometric average, so it is not the same as the arithmetic mean of monthly changes.

Worked example

Monthly recurring revenue went from 12000 to 31500 over 12 months. Step 1: 31500 ÷ 12000 = 2.625, so the multiple is 2.63x. Step 2: total growth is (2.625 − 1) × 100 = 162.50%. Step 3: take the 12th root of 2.625, which is about 1.0837, and subtract 1. The compound monthly growth rate is 8.37%. Growing 8.37% every month for 12 months turns 12000 into 31500.

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Common mistakes

  • Counting both end months. From the value at the end of January to the value at the end of December is 11 months, not 12; using 12 understates the rate.
  • Averaging the monthly growth percentages instead. A +50% month followed by a -50% month averages to zero but leaves you 25% lower; CMGR captures that.
  • Treating the total growth line as the monthly rate. 162.50% is the change over the whole period, 8.37% is per month.
  • Using a start value of zero, for example the first month of a new product. The tool gives no result because growth from zero is undefined; start from the first month with real numbers.
  • Mixing metrics, such as starting with revenue and ending with revenue after a refund policy change. Both values should be measured the same way.

About this calculator

The compound monthly growth rate (CMGR) is the monthly equivalent of CAGR: the smoothed, constant monthly rate that, if applied every month, would take a starting value to an ending value over a given number of months, accounting for compounding rather than simply averaging the monthly changes. It is calculated as (ending value ÷ starting value) raised to the power of (1 ÷ number of months), minus one.

CMGR is especially common in startup and SaaS reporting, where month-to-month revenue or user growth is often too noisy to interpret directly — a single strong or weak month can distort a simple average — so founders and investors use CMGR to express growth as one clean, comparable figure across pitch decks and board reports. Start value, end value and the number of months between them give CMGR, the steady month-on-month rate that would take you from one to the other.

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