Kanban Calculation

Kanban Card"That’s not the formula I use" was the start of the debate. So looking at a few refernce books and searching the web here’s what I’ve come up with. How can something so simple have so many variations?  Let us count the ways …

 

 

1. No. of kanban = (DD*LT+SS*SQRT(LT/TB))/KB+(DD*EPEI)/KB

  • Where: DD = Daily demand (units)
  • LT = Replenishment leadtime (days)
  • SS = Statistically calculated safety stock (units)
  • SQRT = Square root
  • TB = Time bucket of the safety stock data points (days)
  • KB = Quantity per kanban (units)
  • EPEI = Supplier’s replenishment interval (days)

2. #KB = (DD*(LT+SS))/KBS +1

  • #KB = Number of Kanbans
  • DD = Daily Demand
  • LT = Lead Time
  • SS = Safety Stock
  • KBS = Kanban Size

3. Total Req’d Inventory = (Average period demand * Replenishment time) + 1 or 2sigma + safety stock

4. Total Req’d Inventory = (Average period demand * Replenishment time) * 1.X   {where X= 20-40%} and the # of bins = TRI / container or bin size

5.  # Kanban = ((AD * RT) + (SF * SD))/SCQ

  • AD = average period demand
  • RT = replenishment time (in the same time bucket as AD)
  • SF = the Z factor, typically 1.645 for 95%
  • SD = demand standard deviation
  • SCQ = the standard container quantity

6.  # Kanban = (average demand during lead time + safety stock) / container quantity
 

7. N = (dL + S)/C

  • N = number of kanban
  • d = average demand per hour
  • L = lead time in hrs
  • S = safety
  • C = container quantity

8. K=((RT * AC)/Cont) * (SF + C)

  • K = number of kanban
  • Cont = contents per kanban
  • RT = replenishment lead time per kanban
  • AC = average consumption per time period
  • SF = safety factor
  • C = constant, default = 1

The one I use is #5.