Run out of solution mid-week and the appointments do not care. Multiply your sessions by the millilitres each one uses, divide by the bottle size, and round up so there is always a full bottle on the shelf.
Twenty sessions at 60 ml each is 1,200 ml — over a 1,000 ml bottle that rounds up to two bottles.
The example
Three periods, each with a session count, millilitres per session, and the bottle size.
| A | B | C | D | E | |
|---|---|---|---|---|---|
| 1 | Period | Sessions | Ml/session | Bottle ml | Bottles |
| 2 | Week | 20 | 60 | 1000 | 2 |
| 3 | Event | 50 | 50 | 1000 | 3 |
| 4 | Slow | 8 | 60 | 1000 | 1 |
The formula
Total solution over bottle size, rounded up so a partial need still buys a whole bottle:
How it works
Total the solution, then convert to whole bottles:
B2*C2multiplies sessions by the millilitres each one uses — the total solution needed./D2divides by the bottle size to get how many bottles that is.ROUNDUP(...,0)rounds up to a whole bottle, because you cannot order a fraction of one.- Millilitres per session rises for full-body dark tans and falls for a light face-and-arms touch-up — use your real average.
Add a spare bottle for busy weeks by adding 1 to the result — a backordered solution should never cancel an appointment.
Try it: interactive demo
Enter the sessions, millilitres per session, and bottle size.
Variations
Keep a spare
Always hold one backup bottle on the shelf.
Solution cost
Multiply the bottles by your cost per bottle.
Pitfalls & errors
Round up, not to nearest. A need of 1.2 bottles still requires a second bottle — rounding to 1 leaves you short partway through the week.
Track your true millilitres per session. A generous full-body application uses far more than a light touch-up, and guessing low is how the last appointment of the week gets a thin coat.
Practice workbook
Frequently asked questions
How much solution does one session use?
Why round up instead of to the nearest bottle?
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