A matrix org chart puts two managers over one person and lives or dies on whether the chart says which of them writes the review. Drawn well it is the only honest picture of a company where work crosses departments. Drawn badly it is a diagram everybody nods at and nobody uses, because the person in the middle still does not know whose priorities win on Thursday afternoon. This page is the drawing rule that fixes that, plus the arithmetic nobody runs before adopting a matrix: on the worked example a 140-person company carries 43 dotted lines, 2.4 for every manager, and about $2,428 a month of standing check-ins.
One solid line, always, and the rule that decides it
The solid line goes to whoever writes the review and approves the leave. Everything else is dotted. This is not a drawing convention, it is the answer to the only question the person in the middle actually needs, and a matrix chart that leaves it ambiguous has failed at the one job that distinguishes it from a project diagram. Write the rule on the chart's key so a new joiner learns it from the chart rather than from getting it wrong.
Count the lines before you commit to the shape
22% of a 140-person company with 1.4 dotted lines each is 43 dotted lines on top of 140 solid ones: 183 reporting relationships on a chart that looks like it has 140. Spread across 18 managers that is 2.4 dotted reports each, on top of their own team of seven. A manager with nine conversations to hold is the real cost of the matrix, and it is worth seeing as a number before it is a complaint.
Price the standing meetings the second line creates
Every dotted line arrives with a check-in. At thirty minutes fortnightly, 43 lines are 46 hours a month of manager time, about $2,428 at a $52 hourly cost, or $29,149 a year. That is not an argument against the matrix; it is the budget for it, and a matrix nobody budgeted for is one where the check-ins quietly stop and the dotted lines become decorative.
Questions people ask about matrix org chart
Which manager wins a disagreement?
The solid line, by definition, and the chart should make that obvious without anybody asking. If the answer is genuinely the dotted one, the lines are the wrong way round.
How many dotted lines is too many?
When the average manager's dotted reports approach their solid ones. On the worked example 2.4 against seven is workable; four against five is a company where nobody has a clear week.
Should the matrix appear on the published chart?
Yes. A matrix that only exists in conversation is one new joiners take months to learn, and it is exactly the knowledge a directory should carry.