Customer Churn Calculator

Given a cohort and how many you lost, this calculator shows the period churn, retention, and — assuming the rate holds — how the cohort decays over the coming year. Useful for forecasting and for sanity-checking LTV assumptions.

Inputs

Customers at start

Customers lost in period

Periods to project

Results

Churn rate

4.0%

Retention rate: 96.0%
Remaining after 12 periods: 161
Half-life (periods to lose 50%): 18.91

Customers remainingEnd: 161.01

Projection assumes churn stays constant — in reality early periods usually churn faster than later ones.

Formula

Churn = Lost ÷ Cohort · Remainingₙ = Cohort × (1 − Churn)ⁿ

FAQ

What's a half-life?

The number of periods until half the cohort is gone. A 4% monthly churn rate implies a half-life around 17 months.

Is constant churn realistic?

As a planning baseline, yes. Mature cohorts often churn slower than new ones, so this projection is conservative for established customers.