In one sentence
A Brainwidth Score is a number from 0 to 100 for how much of one full day’s mental energy an event or task will take. Scores add up to a day’s capacity, where 100% is a full day.
Brainwidth and mental bandwidth
Mental bandwidth is how much attention and energy you have for thinking, deciding and dealing with people on a given day. It runs out, and a gap in the calendar doesn’t refill it. A Brainwidth Score is a way to budget it: every item gets a share of one full day, and the total shows when you’ve planned more than you have. The word itself is old hacker slang; the Jargon File defines brainwidth as the human version of bandwidth.
The scale
100 is a full day of mental energy. 0 means unscored, so the item doesn’t count. Most single events land under 40. Auto Estimate is calibrated to these:
| Activity | Score |
|---|---|
| Quick email or message check, 15 minutes | 2–5 |
| Team meeting, 1 hour | 10–18 |
| Focused deep work, 2 hours | 18–28 |
| High-stakes presentation, 1 hour | 25–35 |
| All-day workshop or offsite | 40–60 |
How scores add up
A day’s scores add up to its capacity, in five levels:
- Unscored items don’t count.
- Tasks count on the day they’re due. Undated tasks don’t count.
- Weekly capacity is 700%, seven full days. Monthly capacity is 100% for each day in the month.
- Routines and goals aren’t scored.
Same hours, different scores
Monday
Errands and admin
Moderate
52%
Email 5, meeting 14, dentist 6, planning 10, pickup 4, groceries 5, soccer 8.
Thursday
High stakes
Full
114%
Deep work 24, 1:1 12, client pitch 30, tough talk 22, side project 26.
Both days have six hours booked. Moving Thursday’s side project to Friday brings it to 88%, back in Good.
How a score gets set
- Assign: drag the slider.
- Auto Estimate: a suggestion from the item’s details, made on your iPhone with Apple Intelligence (or a built-in formula on iPhones without it). It learns from your corrections.
- Do Not Assign: the item never counts.
What it isn’t
- Not a medical measure. It’s your own planning estimate.
- Not universal. The same meeting can be a 10 for you and a 30 for someone else.
- Not a hard limit. Days past 100% happen. Several in a row is the pattern to watch.
- Not shared. Scores stay on your iPhone and aren’t written to your calendars.
Keep going
- Score your own day with the free calculator
- How to plan your day by mental energy, with sources
- Support guide for everything else