Estimate how long your spa treatment product inventory will last based on container size, measured use per service, waste, and daily demand. The result converts current stock into usable milliliters, service capacity, days of supply, and an estimated 30-day container requirement. It can support reorder timing and reveal how small changes in dispensing affect inventory consumption.
Days of supply estimates when current inventory would be consumed if average usage and daily volume continue. It is not a reorder point because delivery lead time and safety stock are not included.
Keep every quantity in the same unit. If the label uses ounces, convert both container size and use per service to milliliters or use ounces consistently.
With three 1,000 mL containers, 25 mL per service, 5% waste, and 6 services per day:
Container size is multiplied by one minus the waste percentage, leaving the quantity expected to reach clients.
Use a measured average from actual services when possible; it produces a more reliable duration estimate.
Services remaining is operational inventory capacity, while days remaining translates that capacity into a reorder timeline.
Include all average daily services that draw from the same container, even if different service types use it.
Yes. Use zero when losses are negligible, but include realistic dispensing, mixing, and residue loss when applicable.
| Output | Calculation basis | Use |
|---|---|---|
| Usable product | Stock after waste | Available quantity |
| Services remaining | Usable ÷ use/service | Service coverage |
| Days of supply | Services ÷ daily volume | Timing estimate |
| 30-day containers | Monthly use ÷ usable/container | Purchase planning |