Acquisition may never be recovered. Compare this estimate with measured retention and include delivery costs in contribution.
Try this with your own numbersFormula and worked example
Payback months = acquisition cost / monthly contribution
| Input | Example |
|---|---|
| Acquisition cost per customer | 300 |
| Monthly contribution per active customer | 75 |
| Calculated result | 4 months |
Choose reliable inputs
Account for delivery time, review work and when you expect to be paid for each engagement. For this bookkeeping service calculation, use time sheets, engagement scopes and invoice ageing and a consistent definition of one client month.
- Staff hours: include the portion belonging to this client month or reporting period, and record where the value came from.
- Software: include the portion belonging to this client month or reporting period, and record where the value came from.
- Review time: include the portion belonging to this client month or reporting period, and record where the value came from.
Use the same currency for every money input. Do not mix weekly costs with monthly revenue, or count the same expense in both an itemised cost and allocated overhead.
What if customers leave before payback?
Acquisition may never be recovered. Compare this estimate with measured retention and include delivery costs in contribution.
Assumes constant contribution and continued customer activity throughout payback.
What if this input changes?
If acquisition cost per customer rises by 10%, this example changes by 0.4 months. This shows the effect of one change; it does not predict what will happen.
Open the calculator, save your baseline, then change the input supported by the least reliable estimate in your records. Compare both scenarios before committing to a price or capacity promise.