With the illustrative inputs below, the result is 300 per month. Setup cost to recover separately: 500
Try this with your own numbersFormula and worked example
Monthly savings = volume × (old unit cost − new unit cost) − extra recurring cost
| Input | Example |
|---|---|
| Monthly purchased units | 200 |
| Current cost per unit | 20 |
| Alternative cost per unit | 18 |
| Extra monthly shipping or service cost | 100 |
| One-time switching cost | 500 |
| Calculated result | 300 per month |
Setup cost to recover separately: 500
Choose reliable inputs
Allow time for preparation, the service itself and cleaning up before the next appointment. For this optometry practice calculation, use appointment history, service durations and supply costs and a consistent definition of one appointment.
- Staff time: include the portion belonging to this appointment or reporting period, and record where the value came from.
- Equipment: include the portion belonging to this appointment or reporting period, and record where the value came from.
- Admin work: include the portion belonging to this appointment 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.
Does the lower unit price always lower total cost?
Shipping, defects, delays, and switching work can offset a lower purchase price. Enter known additional costs.
Assumes equivalent quality and availability; setup cost is displayed separately rather than amortized.
What if this input changes?
If monthly purchased units rises by 10%, this example changes by 40 per month. 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.