🔀 Context Switching Cost Calculator
A context switching cost calculator using Gloria Mark's (UC Irvine) measured 23-minute-15-second average interruption recovery time, not a guessed number.
Default of 23.25 minutes is Gloria Mark's (UC Irvine) measured average time to resume same-day interrupted work.
What Context Switching Cost Calculator Does
Most "cost of interruptions" figures circulating online are unsourced round numbers. This calculator instead defaults to a measured figure: in a study of 36 managers, analysts, developers and engineers shadowed for three days, Gloria Mark and colleagues at UC Irvine found that interrupted work resumed the same day — 81.9% of it was — took an average of 23 minutes and 15 seconds to pick back up. That number comes from a June 2006 Gallup interview with Dr. Mark describing the study directly, not a secondhand paraphrase.
The same research found something easy to miss in the headline figure: people interrupted themselves almost as often (about 44% of the time) as they were interrupted by someone else, and workers switched "working spheres" on average every 10 to 12 minutes — far more often than the 23-minute number alone suggests. This calculator asks for meaningful interruptions specifically (the ones that actually require the 23-minute reorientation), not every micro-switch, which is why the default switch count is modest rather than matching that 10-minute figure literally.
A separate, widely cited rule of thumb comes from software management writer Gerald Weinberg's Quality Software Management: Systems Thinking: adding a second concurrent project costs roughly 20% of a person's time to context-switching overhead, and a third project pushes that toward 40%. It is a practitioner heuristic rather than an empirical study like Mark's, useful for a different question — the cost of juggling projects, not the cost of interruptions within one.
How to Use Context Switching Cost Calculator
- Enter how many people are affected and how many meaningful interruptions each has per day
- Adjust the recovery time per interruption if you have your own data, or keep the Gloria Mark default
- Enter hourly rate and working days to see the daily and annual cost
Formula Used by Context Switching Cost Calculator
Annual cost of context switching
Annual cost = switches/day × recovery_minutes ÷ 60 × hourly_rate × people × working_days/year
- switches/day
- Meaningful interruptions per person per day
- recovery_minutes
- Average time to resume the original task (default: 23.25 minutes, from Gallup's interview with Gloria Mark)
Worked example
1 person, 6 switches/day, 23.25 minutes recovery, $50/hr, 250 working days
- 6 × 23.25 = 139.5 minutes/day = 2.325 hours/day
- 2.325 × $50 = $116.25/day
- $116.25 × 250 days = $29,062.50/year
Result: $29,062.50 estimated annual cost for one person
Weinberg's concurrent-project overhead (widely cited rule of thumb)
From Gerald Weinberg's Quality Software Management: Systems Thinking, as commonly reproduced and corroborated across multiple independent sources.
| Concurrent projects | Approx. time lost to switching |
|---|---|
| 1 | 0% |
| 2 | ~20% |
| 3 | ~40% |
| 5 | ~75% |
Source: Coding Horror — "The Multitasking Myth" (Jeff Atwood)
How to Read Your Result
The 23-minute figure is a same-day-resumption average, not a worst case
It describes work that was picked back up the same day (81.9% of interrupted work was); work that spills to the next day likely carries a larger real cost that this figure does not capture.
Recovery time is reorientation cost, not 100% lost output
People often do other useful things during the reorientation window — this is time to get back to the original task's mental state, not necessarily 23 minutes where nothing happens at all.
Limitations & Accuracy Notes
- The default recovery time is a research average from one workplace study of 36 knowledge workers in 2005 — actual recovery time varies by role, task complexity, and individual.
- This model treats every switch as equally costly; in reality, a switch to a closely related task likely costs less than a switch to something completely different (the same research found this distinction between "interaction" and "distraction" interruptions).
- It does not model the compounding effect of running low on focus later in the day after many earlier switches.
Frequently Asked Questions
Where does the 23-minute default come from?
Why is the default number of switches per day set so low?
Does this account for people switching between more than 2 tasks?
Is 23 minutes really lost, or can some of it overlap with other work?
Is my data stored?
References & Further Reading
- Gallup Business Journal — "Too Many Interruptions at Work?" (Q&A with Gloria Mark, PhD, UC Irvine) — Source of the 23-minutes-15-seconds same-day resumption average, the 81.9% same-day figure, and the 44% self-interruption figure used above
- Coding Horror — "The Multitasking Myth" — Describes Weinberg's concurrent-project context-switching overhead rule of thumb used in the table above