Formula
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
- New-customer count must correspond to new customers included in ending count. Cohort returns and reactivations need a consistent definition.
Example Calculation
- Customers at start: 100
- Customers at end: 110
- New customers during period: 20
Customers at start = 100; Customers at end = 110; New customers during period = 20. The primary result is 90.
Frequently asked questions
How do I use this calculator?
Enter customers at start, customers at end, new customers during period. The result updates automatically. Use Reset to restore the example values.
What method does it use?
retention=(end−new)/start.. New-customer count must correspond to new customers included in ending count. Cohort returns and reactivations need a consistent definition.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.