A swim class with one empty spot looks fine on the schedule and costs exactly one tuition. Multiply that across a session and the gap is usually larger than any price increase you were considering. Two columns turn “we are pretty full” into a number the schedule can be built around.
A four-swimmer Level 2 class with three enrolled is 75% full — and $128 of tuition sitting in an empty lane.
The example
Three classes in the same eight-week session, priced per swimmer.
| A | B | C | D | E | F | G | |
|---|---|---|---|---|---|---|---|
| 1 | Class | Capacity | Enrolled | Tuition | Fill rate | Empty seats | Revenue gap |
| 2 | Parent & Tot | 6 | 5 | $96 | 83.3% | 1 | $96 |
| 3 | Level 2 | 4 | 3 | $128 | 75.0% | 1 | $128 |
| 4 | Level 4 | 4 | 4 | $144 | 100.0% | 0 | $0 |
The formula
Two independent columns from the same three inputs:
How it works
Why both columns are worth having:
C2/B2is the fill rate. Format it as a percentage and it is instantly comparable across classes with different capacities — a 5-of-6 and a 3-of-4 are not the same class, and the ratio says so.B2-C2is empty seats. Whole numbers, and the only column an instructor actually cares about.*D2prices the gap. This is the column that changes decisions, because “one empty spot” and “$128” feel completely different in a scheduling meeting.- Sum the gap column across the session. That total is what a class-consolidation or a waitlist-conversion push is actually worth.
Do not treat every empty seat as recoverable. Some classes are capped by instructor ratio and some by lane space; the gap is an upper bound on the opportunity, not a forecast.
Try it: interactive demo
Enter the class capacity, current enrolment and the session tuition.
Variations
Session-wide fill rate
Sum enrolled over sum capacity rather than averaging the per-class rates — averaging percentages weights a 2-seat class the same as a 12-seat one.
Classes worth consolidating
Flag any class under a threshold so the schedule review has a short list instead of a spreadsheet.
Pitfalls & errors
Capacity is a policy number, not a pool number. If the ratio rule says four swimmers to one instructor at Level 2, capacity is four even when the lane could hold six — entering the physical maximum overstates the gap on every row.
Track fill rate by time slot, not just by level. The 4:30 classes are usually full and the 11:00 classes usually are not, and that pattern is a scheduling fix rather than a marketing one.
A zero capacity gives #DIV/0!. Wrap the fill rate in IFERROR if the sheet has placeholder rows for classes that have not been sized yet.
Practice workbook
Frequently asked questions
Is a 100% fill rate the goal?
Should the revenue gap include the instructor cost I saved?
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