How many people could your project lose — to a bus, a better offer, a long holiday — before some part of it has nobody left who knows it? Map who knows what, and this finds the answer: the fewest departures that leave an area orphaned, plus which areas and which people are the single points of failure.
People
A
B
C
D
Who knows what
— none1 learning2 knows3 owns
Area × personRate each person's depth in each area: — none, 1 learning, 2 knows it, 3 owns it. Someone counts as able to keep an area alive on their own at depth 2 or more; “learning” is bench strength but can't hold it alone yet. The bus factor is the fewest such knowers any one area has.
A
B
C
D
depthHow many people could keep this area alive on their own (depth ≥ 2). 0 is a gap nobody owns; 1 is a single point of failure; 2+ has a backup.
3
2
—
—
2
3
1
—
—
1+1
3
—
1
—
1+1
—
2
2
1
2+1
—
—
3
2
2
1
—
—
3
1+1
1bus factor
Your bus factor is 1. Lose the wrong person and 3 areas (Billing, Infra / deploy, Data model) loses its only owner. The most exposed is Ana — gone, and 2 areas go dark at once.
Where it's thinowners per area
Billing
1 owner +1 learning
Infra / deploy
1 owner +1 learning
Data model
1 owner +1 learning
Auth
2 owners
Search
2 owners +1 learning
Mobile app
2 owners
Who's hard to replaceareas orphaned if they leave
AAna
2 areas dark · owns 3
DDev
1 area dark · owns 2
These people are the only ones at working depth in some area — the quickest way to raise your bus factor is to get a second person to depth 2 in the areas above.
bus factor = the fewest people whose loss leaves an area with no owner · depth is your honest read, so the number is only as good as it