How to calculate churn rate, step by step
The churn rate is one division that answers one question: what share of your customers left? A business owner who knows the answer can see whether the customer base is holding steady or quietly shrinking, and how many new customers must arrive just to stand still. The calculation needs two numbers: the starting customers and the lost customers. The answer is a percent: a churn rate of 5.00% means 5 of every 100 starting customers left, and a retention rate of 95.00% means 95 of every 100 stayed.
The formula is churn rate = lost customers ÷ starting customers × 100. The starting customers are how many customers you had at the start of the period — every customer on the books on day one, before a single one leaves. The lost customers are how many of those starting customers left in the period — cancellations, lapses, accounts closed, all added up. The retention rate is the complement: retention rate = 100 − churn rate. Both figures are counts of customers, for the same period, or the rate is wrong before it starts.
The worked example, line by line. Step 1 — the starting customers: 1,000. Step 2 — the lost customers: 50. Step 3 — the division: 50 ÷ 1,000 = 0.05. Step 4 — the percent: 0.05 × 100 = 5.00%. Step 5 — the retention rate: 100 − 5.00 = 95.00%. Step 6 — the meaning: 5 of every 100 starting customers left, and 95 of every 100 stayed. Work it yourself in the churn rate calculator.
What the number means
A rate of 5.00% means 5 of every 100 starting customers left, so on 1,000 starting customers the business keeps 950 and must replace the 50 it lost just to stand still — for every 100 customers at the start, 95 are still there at the end and 5 have gone. A higher rate means more of the base is leaving: the business must win more new customers to hold its ground, and the cost of winning them eats into the profit the base brings in. A lower rate means more of the base is staying: the business keeps the customers it already paid to win, and each new customer adds to the base instead of replacing a leaver. The rate on its own never says whether 5.00% is healthy or thin — that depends on how fast new customers arrive and on the industry. A business with fast sign-ups can thrive at a rate that would shrink a business with slow sign-ups. What the rate does say, plainly, is what share of your starting customers left.
What moves the churn rate
Two things move the rate: the lost customers and the starting base. Raise the lost customers and the rate rises, because more leavers are now a bigger share of the same base: with the starting base held at 1,000, 100 lost customers puts the rate at 10.00% — the smallest lost customers for the rate to reach 10.00% is 100 — and 25 lost customers puts it at 2.50%. Cut the lost customers and the rate falls. Raise the starting base and the rate falls, because the same leavers are now a smaller share of a bigger base: with the lost customers held at 50, 2,000 starting customers puts the rate at 2.50%. Cut the starting base and the rate rises. Note the asymmetry: losing customers hurts twice — the base shrinks, so the next leaver is a bigger share of what is left — and a rate that rises month after month is a warning even before it passes 10%.
Churn rate benchmarks
Churn rate benchmarks, as general guidance only: below 2% is excellent — SaaS-style businesses run here, where the product is sticky and the customers stay year after year. From 2% to 10% is a common middle — 5% sits in the middle of it, a normal rate for many subscription businesses, where each month leaves a real share of the base to replace. Above 10% is a warning sign — the business is losing a tenth of its base in a single period, and it must win new customers faster than it loses old ones just to stand still. These are rules of thumb, not lender rules: what counts as healthy depends on the industry, the customer mix and how fast new customers arrive, and a high rate with fast sign-ups can be a better business than a low rate with no sign-ups at all.
When the churn rate is undefined
If the starting customers are 0, the rate is undefined — the starting base is 0, and dividing by 0 has no answer. A business with no customers at all has no rate to calculate, only a warning. If the lost customers are 0, the rate is 0.00% — a real figure, not undefined: on 1,000 starting customers the churn rate is 0.00%, because nobody left. If the lost customers are above the starting customers, the rate goes above 100% — more customers left than started, possible only if the count mixes cohorts, and the calculator shows it rather than capping it.
Common mistakes
The first mistake is confusing the churn rate with customer acquisition cost — that one is the cost of winning new customers, the opposite side of the funnel, so it answers a different question. The same 1,000 starting customers and 50 lost give a churn rate of 5.00%, and mixing the two up turns a leaving-customers question into a winning-customers question. The second is confusing churn with retention — retention is the complement, 100 minus the churn rate, so a churn rate of 5.00% is a retention rate of 95.00%, and quoting one as the other flips the story. The third is using the wrong starting base — counting customers who joined mid-period as if they were there at the start, or leaving out a whole segment — and the rate is wrong before it starts. The fourth is forgetting the rate moves — a rise in leavers pushes the rate up without a single new customer being lost. Work it out in the churn rate calculator, and check the customer acquisition cost calculator and the customer lifetime value calculator before you decide what the churn means.