How does work flow?

Little's Law ties three flow numbers into a single equation: how much work is in progress, how fast you finish it, and how long each item takes to get through. Fix any two and the third is forced โ€” including the headline lesson that, at a steady pace, the only way to finish sooner is to start less.

Solve for
Work in progressWork in progress: the number of items started but not yet finished โ€” everything currently in flight at once.
items
=
ThroughputThe rate at which items are finished โ€” how many leave the system per unit of time.
/
ร—
Cycle timeHow long a single item takes to get through, from the moment work starts on it to the moment it's done.
2

Each item spends about 2 weeks in progress, from start to finish.

Little's Law holds on average in a stable system โ€” one where work arrives about as fast as it's finished and the queue isn't growing.

What if
Work in progressCycle time
6 items
1 week
9 items
1.5 weeks
12 itemsnow
2 weeks
18 items
3 weeks
24 items
4 weeks

Hold the finishing pace steady and cycle time tracks WIP one for one: halve what's in progress and each item ships in half the time. That's the whole case for WIP limits.

based on Little's Law