The Office Availability Math
Two people in the same office are available to each other far less than you'd think. The math explains why DIY tools were liberating.
The claim in The Return of the Assistant is that two people working the same 9-5 schedule in the same office are only available to each other about 80% of the time. That’s the generous number. The real availability for synchronous handoff is much lower.
Annual Overlap: Days Both Present
Start with a standard work year:
- Working days: ~260 per year (52 weeks × 5 days)
- Holidays: ~10 days (both absent, so no impact on overlap)
- Sick days: ~5 days each per year
- Vacation: ~10-15 days each per year
If Person A takes 5 sick days and Person B takes 5 sick days, and these don’t overlap, that’s 10 days where one is absent. Similarly for vacation—call it 20 days of non-overlapping absence between the two.
Result: ~230 days where both are present out of ~250 working days (after holidays). That’s ~92% annual overlap on days present.
The 80% figure in the main essay is actually conservative for this factor alone.
Daily Overlap: Hours Both Available
Here’s where the math gets worse. Being in the same building isn’t the same as being available to each other.
A typical 8-hour workday:
| Activity | Person A | Person B | Overlap Lost |
|---|---|---|---|
| Lunch | 12-1pm | 12:30-1:30pm | 1 hour |
| Meetings | 2 hours | 2 hours | 2-3 hours (different meetings) |
| Focus time | 1 hour | 1 hour | 1-2 hours (don’t interrupt) |
| Breaks/coffee | 30 min | 30 min | 30 min |
| Bathroom/errands | 20 min | 20 min | 20 min |
Even if both people are “at work,” their available windows don’t align. Person A is free 10-11am; Person B is in a meeting. Person B is free 2-3pm; Person A is heads-down on a deadline.
Conservative estimate: Of an 8-hour day, perhaps 4-5 hours have any potential for overlap. But the windows shift independently, so actual aligned availability might be 3-4 hours—roughly 40-50% of the workday.
Combined Availability
Multiply the factors:
- Annual overlap (days both present): ~90%
- Daily overlap (hours both available): ~45%
- Combined: ~40% of nominal work time
Two people with the same schedule, in the same office, working on the same projects, are actually available to each other less than half the time.