Swim lessons run on strict instructor ratios, so a level with 23 swimmers and six per class needs four classes, not 3.83. Rounding up gives the classes to schedule, and the leftover capacity shows how many late sign-ups you can still take.
23 swimmers at six per class need 4 classes with 1 open spot.
The example
Three worked examples. Change any yellow input in the practice workbook and the results recalculate.
| A | B | C | D | E | |
|---|---|---|---|---|---|
| 1 | Case | Swimmers | Max per class | Classes | Open spots |
| 2 | Tadpoles | 23 | 6 | 4 | 1 |
| 3 | Minnows | 29 | 8 | 4 | 3 |
| 4 | Sharks | 17 | 5 | 4 | 3 |
The formula
Here is the formula, built directly from the inputs:
How it works
Here is the logic, one piece at a time:
B2/C2is the fractional classes.ROUNDUP(...,0)schedules whole classes.D2*C2is total capacity.- Subtract
B2for open spots.
Keep every number in its own input cell so the formula never needs editing.
Try it: interactive demo
Enter the values below.
Variations
Instructor hours
Classes times 0.5 hour.
Fill rate
Share of capacity used.
Pitfalls & errors
Use ROUNDUP, not ROUND, or a level may end up with too few classes.
Ratios differ by level; keep a max per level.
Open spots feed your waitlist message.
Practice workbook
Frequently asked questions
What if a class is nearly empty?
Can I mix levels?
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