With the illustrative inputs below, the result is 220 per referred sale.
Try this with your own numbersFormula and worked example
Retained contribution = revenue × contribution margin − reward − program cost
| Input | Example |
|---|---|
| First-sale revenue | 800 |
| Contribution margin | 40 % |
| Referral reward | 75 |
| Program cost per sale | 25 |
| Calculated result | 220 per referred sale |
Choose reliable inputs
Account for turnaround, maintenance and available inventory before accepting another booking. For this tool rental calculation, use rental contracts, asset records and maintenance logs and a consistent definition of one rental booking.
- Inspection: include the portion belonging to this rental booking or reporting period, and record where the value came from.
- Repair: include the portion belonging to this rental booking or reporting period, and record where the value came from.
- Counter staffing: include the portion belonging to this rental booking 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.
Should rewards be compared with revenue or contribution?
Compare with the contribution remaining after delivering the sale. Revenue alone overstates the amount available for rewards.
Excludes lifetime repeat purchases and any tax treatment of rewards.
What if this input changes?
If first-sale revenue rises by 10%, this example changes by 32 per referred sale. 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.