The Office Availability Math: Why In-Person Work Helps Less Than You Think

Two people in the same office are available to each other far less than most assume. The math explains why.

The Return of the Assistant uses 80% as an estimate of mutual availability for two people on the same 9–5 schedule in one office. That is generous; actual availability for a 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

People in the same building may still be unavailable to each other.

A typical 8-hour workday:

Available periods differ even when both people are at work. Person A may be free from 10–11am while Person B attends a meeting; Person B may be free from 2–3pm while Person A works 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.