Before I continue, here's a quick refresher on the terms that I'm using. If you're a SaaS metrics pro you can skip the next two paragraphs.
Your account churn rate, also called "customer churn rate" or "logo churn rate", measures the rate at which your customers are canceling their subscriptions. If you have, say, 1,000 customers on February 1st and by the end of the month 30 of them have canceled, your account churn rate is 3% p.m. in Feburary. Note that this assumes that all 1,000 customers are on monthly plans and can cancel that month – if some of your customers are on annual plans, you need to calculate the churn rate of that customer segment separately.
Your MRR churn rate, sometimes also referred to as "dollar churn rate", is the rate at which you are losing MRR through downgrades and cancelations. If you have, for example, $100,000 in MRR on February 1st, and by February 28 you've lost $4,000 of these $100,000 due to downgrades and cancelations, your gross MRR churn rate is 4% in February. Assuming you have $6,000 in expansion MRR in the same month – i.e. an increase in MRR of existing customers, e.g. due to upgrades to more expensive plans or additions of seats – your net MRR churn is minus $2,000 and your net MRR churn rate is minus 2% in that month. For more details on these and other SaaS metrics, check out ChartMogul's SaaS Metrics Cheat Sheet.
Thanks for your attention, SaaS metrics newbies, and welcome back pros. The following two charts show the disastrous effect of MRR churn, using an imaginary SaaS startup (let's call it Zombie.com) with $100,000 in MRR that has a net MRR churn rate of 3% p.m. and is adding $10,000 in MRR from new customers each month:
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| MRR development of Zombie.com - click for a larger version |
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| MRR development of Zombie.com - click for a larger version |
The first chart shows how much new MRR from new customers Zombie.com is adding (light green), how much MRR it's losing due to churn (red) and what the net change is (dark green). The second chart shows the resulting MRR (blue) and the ratio between new and lost MRR (orange), inspired by Mamoon Hamid's great "Quick ratio" of (Added MRR / Lost MRR), which I recently learned about.
As you can see in these two charts, not only does the net new MRR of Zombie.com go down every month. It actually asymptotes to zero, which means that the company is hitting a wall at around $350,000, at which it stops growing.
The math behind this is of course trivial, since the assumption was that the company is adding a constant dollar amount of MRR every month, while churn MRR, being a constant percentage of total MRR, is growing. So what happens if instead of acquiring new customers linearly, you manage to add new MRR from new customers at an ever increasing rate?
Here's another imaginary SaaS startup, let's call this one Treadmill.io. Like Zombie.com, Treadmill.io has $100,000 in MRR in the beginning of the timeframe that I'm looking at and has a net MRR churn rate of 3% p.m. Unlike Zombie.com, Treadmill.io is adding new MRR from customers at an accelerating rate, though: In the first year it's adding $10,000 per month, in the second year $15,000 per month, then $20,000 per month, and so on. Let's look at the charts for Treadmill.io:
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| MRR development of Treadmill.io - click for a larger version |
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| MRR development of Treadmill.io - click for a larger version |
The MRR development of this company looks much less depressing, and after ten years it reaches close to $1.5M in MRR. However, as you can see in the first chart, as well as in the declining orange line in the second chart, churn is eating up an ever increasing part of the new MRR coming in from new customers. If Treadmill.io doesn't manage to decrease churn, it will have to acquire more and more new customers just to offset churn, and keeping net new MRR growth up might become increasingly difficult.
OK, but what if you're acquiring new customers at an exponential growth rate? Let's look at a third imaginary company called Weed, Inc. Like Zombie.com and Treadmill.io, Weed starts with $100,000 in MRR and has a net MRR churn rate of 3% p.m. The big difference is that Weed is adding new MRR from new customers at an exponential rate. Starting with $10,000 in the first month, the company is growing new MRR from new customers 10% m/m in the first year; 8% m/m in the second year; 6% m/m in year three; 4%, 3% and 2% in year four, five and six, respectively; and 1.5% from year seven onwards.
Here are the charts for Weed, Inc:
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| MRR development of Weed, Inc. – click for a larger version |
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| MRR development of Weed, Inc. - click for a larger version |
Not much to complain about: After ten years, Weed, Inc. has more than $19M in MRR. The big question, though, is if a development like this is realistic. In order to offset ever increasing churn amounts, Weed needs to acquire new MRR from new customers at an extremely ambitious pace. In the last month of the ten year model that I'm looking at, Weed adds about $870,000 in new MRR from new customers, almost 5% of the company's total MRR at the beginning of that month. To acquire so many new customers, Weed needs either a viral product (very rare in B2B SaaS) or extremely scalable lead acquisition channels.
I'm not saying that it's impossible, but I believe the much more likely path to a SaaS unicorn is by getting MRR churn to zero or below – which means you have to make your product more and more valuable for your customers and acquire larger and larger customers over time.
