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Customer Retention & Attrition Calculator

Separate retained customers from new arrivals when comparing customer counts.

  • Formula & worked example
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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Edit a calculated value to solve backwards, or lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Use the result with context

Results are estimates for planning and education. Confirm rates, taxes, fees, and legal requirements with the relevant institution or a qualified professional before making a financial decision.

Formula and method

Subtract new customers from the ending count, then divide by the starting count. This estimates the share of the starting customer base retained over the period.

Retention (%) = (ending customers − new customers) ÷ starting customers × 100

Worked example

Enter these known values and leave the other values blank.

Existing customers
100
Total customers
110
New customers
20
Attrition rate
10 %
Customer retention rate
90 %

Assumptions and limitations

  • Inputs describe one consistent reporting period. Review the formula and counting conventions before comparing results.

Common questions

Can customer count grow while retention falls?

Yes. New arrivals can outweigh losses from the starting customer base. Overall growth and retention describe different aspects of that change.

References

The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.

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