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Customer Retention Calculator.

Calculate period retention and churn from opening, acquired, and closing customers.

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Retained customers: 900

Retained customers

900
Churned customers: 100

Churned customers

100
Retention rate: 90%

Retention rate

90%
Churn rate: 10%

Churn rate

10%

Retained = closing − acquired; retention and churn are complementary rates for the opening cohort.

FAQs

What is the retention formula?

Retained customers equal closing customers minus customers acquired during the period; retention divides retained by opening customers.

How to Use the Customer Retention Calculator

Estimate retained customers, churn, and rates for one defined cohort period.

  1. Enter opening customers at the start of the period.
  2. Enter customers acquired during the period.
  3. Enter the closing customer count.
  4. Review retention and churn as percentages of the opening cohort.

Retention and Churn Formulas

Retained customers

Retained = Closing customers − Acquired customers

The calculation assumes acquired customers are new additions during the period.

Retention rate

Retention = Retained ÷ Opening customers × 100

Churn is the complementary share of the opening cohort.

Real-World Use Cases

Cohort Review

Track customer continuity over a month, quarter, or year.

Service Planning

Pair retention with acquisition to understand net customer change.

Tips

Tips

  • Define the period and customer definition consistently.
  • Separate logo retention from revenue retention when account sizes vary.

Common Mistakes to Avoid

  • Counting acquired customers as retained opening customers.
  • Mixing different cohort periods.

Related Calculators

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Cite this calculator

Canonical URL: https://mathify.one/en/business/customer-retention

Cite as: Mathify. (2026). Customer Retention Calculator. https://mathify.one/en/business/customer-retention

Use Cases

Measure cohort loyalty

Track how well you keep customers over a specific period by comparing opening and closing numbers, excluding new acquisitions.

Example: If you start with 500, acquire 100, and end with 550, retained = 450, retention = 90%.

Evaluate churn impact

Quantify customer loss to identify trends and inform retention strategies.

Example: A churn rate of 10% means you lost 10% of your opening customers.

Frequently Asked Questions

How is the retention rate calculated?
The retention rate is calculated by dividing the number of retained customers (closing customers minus acquired during period) by the opening customers, then multiplying by 100. This gives the percentage of the original cohort that stayed.
What is the churn rate formula?
The churn rate is the complement of the retention rate: 100% minus the retention rate. It represents the percentage of opening customers lost during the period, excluding new acquisitions.
What does 'retained customers' mean?
Retained customers are those from the opening cohort who remain at the end of the period. It is calculated as closing customers minus acquired during period, assuming no other changes.

Tips & Common Mistakes

Tips

  • Use consistent time periods (e.g., monthly, quarterly) for accurate comparisons.
  • Ensure 'acquired during period' includes only new customers, not re-engagements.
  • Track retention and churn rates over multiple periods to spot trends.
  • Combine with customer lifetime value to assess the financial impact of churn.

Common Mistakes to Avoid

  • Including acquired customers in the retained count, which inflates retention.
  • Using closing customers as the denominator instead of opening customers.
  • Ignoring that churn rate is the inverse of retention rate, not a separate calculation.

Last updated: August 13, 2026