This document discusses concepts related to flow and Little's Law using a bar analogy. It defines work in progress (WIP), lead time, cycle time, and throughput in the context of bottles of whiskey at a bar. It then applies Little's Law to calculate that with 12 bottles at the bar, a throughput of 6 bottles/year, the average lead time for a bottle must be 2 years. It also shows that cycle time is the inverse of throughput. The document concludes by asking questions about how the metrics would change if the bar size, bottle size, or throughput were altered.

1. John Little,
whiskey and flow
Paulo Caroli Agile Coach
pcaroli@thoughtworks.com
Twitter: @paulocaroli

2. Agenda
• Flow numbers at the bar
• Flow numbers at the Kanban board
• Little’s Law
• Q&A

3. Agenda
• Flow numbers at the bar
• Flow numbers at the Kanban board
• Little’s Law
• Q&A

4. Flow numbers at the bar

5. WIP
• The number of bottles in the bar. Bottles
that have been opened, but not yet
empty.

6. Lead time
• The time between the bottle is added to
the bar and the bottle comes out of the
bar (empty).

7. Cycle time
• The time between two successive empty
bottles leaving the bar

8. Throughput
• The rate at which bottles are passing through
the bar.

9. Batch size
• The size of the bottles.

10. Agenda
• Flow numbers at the bar
• Flow numbers at the Kanban board
• Little’s Law
• Q&A

11. Agenda
• Flow numbers at the bar
• Flow numbers at the Kanban board
• Little’s Law
• Q&A

12. Flow numbers at the Kanban board

13. To Do Doing Done
12
10 1
John
7
5
4
9 Suzy
21 18
31
Paul
17
5 Amy

14. To Do Doing Done
WIP
12
10 1
John
7
5
4
9 Suzy
21 18
31
Paul
17
5 Amy

15. To Do Doing Done
Day 6
Day 1 12 10
10 10
John 1
7 Lead Time
5
4
9 Suzy
21 18
31
Paul
17
5 Amy

16. To Do Doing Done
Cycle time
12
10 1
John Day 1
7
Day 2 5
4
9 Suzy
21 Day 3 18
31
Paul
17
5 Amy

17. To Do Doing Done
12
10 1
John
7
5
4
9 Suzy
21 18
31
Paul
17
Throughput
5 Amy

18. To Do Doing Done
12
10 1
John
Batch size
7 5
4
9 Suzy
21 18
31
Paul
17
5 Amy

19. Agenda
• Flow numbers at the bar
• Flow numbers at the Kanban board
• Little’s Law
• Q&A

20. Agenda
• Flow numbers at the bar
• Flow numbers at the Kanban board
• Little’s Law
• Q&A

21. Little’s Law

22. To Do Doing Done
WIP
12
10 1
John
7
5
4
9 Suzy
21 18
31
Paul
17
5 Amy

23. To Do Doing Done
WIP
12
10 Demand Throughput
1
John
7
5
4
9 Suzy
21 18
31
Paul
17
5 Amy

24. To Do Doing Done
WIP
12
10 1
John
7
5
4
9 Suzy
21 18
31
Paul Lead Time
17
5 Amy

25. To Do Doing Done
WIP
12
10 1
John
7
5
4
9 Suzy
21 18
31
Paul Lead Time
17
5 Amy
# WIP is proportional to average lead time

26. “The average number of work
items in a stable system is equal
to their average completion rate,
multiplied by their average time
in the system.”
John Little, 1961

27. WIP = Throughput x Lead time

28. The numbers at my bar
• My bar has 12 bottles of whiskey
• I finish an average of 6 bottles per year
• What is the average lead time for a bottle of
whiskey?

29. ?

30. WIP = Throughput x Lead time
12 b= 6 b / year x Lead time
Lead time = 2 years

31. Cycle time is the inverse of
Throughput

32. WIP = Throughput x Lead time
<=>
Lead Time = WIP x Cycle Time

33. Lead Time = WIP x Cycle Time
2 years = 12 b x Cycle time

34. Cycle time = 1 year / 6 b

35. Converting to months…

36. Cycle time = 2 months / 1 b

37. In average, I finish a bottle every
2 months

38. Agenda
• Flow numbers at the bar
• Flow numbers at the Kanban board
• Little’s Law
• Q&A

39. Agenda
• Flow numbers at the bar
• Flow numbers at the Kanban board
• Little’s Law
• Q&A

40. Questions to the audience
• What happens if my bar size reduces by half?
• What if I only buy small bottles (half size)?
• What if I double my drinking average?
• Q&A

41. John Little,
whiskey and flow
Paulo Caroli Agile Coach
pcaroli@thoughtworks.com
Twitter: @paulocaroli

42. Thank you!
Questions?
feedback please: @paulocaroli
www.KanbanAndBeyond.com
Paulo Caroli Agile Coach
pcaroli@thoughtworks.com
Twitter: @paulocaroli