SaaS Churn Rate Impact Calculator

About this calculator

Model customers and monthly recurring revenue remaining after monthly churn. Explore a fixed starting cohort with constant ARPU and no new customers.

How to use

Enter whole starting customers, monthly average revenue per customer in USD, monthly customer churn percentage, and whole months. Select Calculate to estimate the ending cohort and monthly recurring revenue (MRR). Reset example restores 1,000 customers, 50 USD ARPU, 5% churn, and 12 months.

How it works and formula

Customers remaining = starting customers × (1 − monthly churn / 100)^months. Ending MRR = customers remaining × ARPU. MRR lost = starting MRR − ending MRR; revenue retained is ending MRR divided by starting MRR. The same retention ratio applies to customers and revenue because ARPU is constant.

Worked example

With 1,000 starting customers, 50 USD monthly ARPU, and 5% monthly churn for 12 months, about 540.36 expected customers remain. Ending MRR is 27,018.00 USD, down 22,982.00 USD from 50,000.00 USD. Revenue retained is about 54.04%.

Assumptions and limitations

This simplified cohort adds no new customers and holds churn and ARPU constant. It excludes expansion, contraction, reactivation, price changes, and seasonality, and does not predict real business performance. Fractional customers are expected values, not literal people; revenue uses the unrounded expected count. Customer count must be a whole number from 1 to 100,000,000; ARPU 0.01–1,000,000 USD; churn 0–100%; and months whole from 0 to 120. Month zero preserves the starting cohort, even at 100% churn. At 100% churn, subsequent months have zero customers.

SaaS churn rate impact FAQ

Does this calculator use customer churn or revenue churn?

The input is monthly customer churn: the percentage of the remaining customer cohort lost each month. It does not accept revenue churn or net revenue retention as a substitute. Revenue follows the customer count only because average revenue per customer stays constant.

Does churn apply to the original customer count every month?

No. Each month’s churn applies to the customers remaining after earlier months. The model compounds retention as starting customers × (1 − monthly churn / 100)^months; it does not subtract the same original customer count each month.

Can I enter an annual churn rate?

The field expects a monthly percentage. Entering an annual percentage directly would model that loss every month. Use a monthly assumption consistent with the scenario you want to explore.

Why can the result show fractional customers?

The remaining customer count is an expected value for a simplified cohort, not a literal count of people or accounts. Revenue is calculated from the unrounded expected count, so rounding customers first may give a different revenue total.

What does monthly ARPU mean here?

It is the assumed monthly average revenue per customer in USD. The model holds it constant for all remaining customers and all modeled months; it does not track different plans or individual customer revenue.

Is ending MRR the total revenue earned over the period?

No. Ending monthly recurring revenue is the modeled monthly revenue at the end of the selected horizon. It is not cumulative revenue across all months, cash collected, or profit.

What does MRR lost measure?

MRR lost is starting MRR minus ending MRR. It compares two monthly revenue levels; it does not add up revenue shortfalls during the intervening months.

Are new customers, upgrades, or reactivations included?

No. This is a closed starting cohort with no acquisition, expansion, contraction, reactivation, price changes, or seasonality. It cannot forecast total business revenue when those factors matter.

What happens at zero months, zero churn, or 100% churn?

Zero months preserves the starting customers and MRR, even when churn is 100%. Zero churn preserves them at every accepted horizon. At 100% monthly churn, any horizon of one month or more leaves zero customers and zero MRR.

Is revenue retained a prediction of net revenue retention?

No. Here revenue retained is ending MRR divided by starting MRR for a fixed-ARPU cohort. It equals customer retention under these assumptions and excludes expansion and contraction. It is a scenario output, not a verified business metric or a guarantee of future performance.

Model review

Reviewed September 26, 2026 against the implemented formula, input rules and worked example. The fixed-churn, fixed-ARPU scenario is a mathematical model, not an external forecast or professional assessment.