How big should a FIFO lane be?

Big enough to cover the longest changeover or breakdown the downstream process should ride through, in whole containers and never fewer than one: use rate × stop minutes ÷ 60, plus a margin. At 64 units an hour and a 40 minute stop that is 42.67 units, or 46.93 with 10%, so 3 containers of 20. No standard gives an exact formula, so this is common practice.

What happens when a FIFO lane is full?

The process feeding it stops until the downstream process takes a unit out and a position frees up. That stop is the pull signal, so the lane needs no card. The Lean Lexicon puts it the same way: if the lane fills up, the supplying process must stop until the customer consumes some.

How is a FIFO lane different from a supermarket or a kanban loop?

A supermarket keeps a separate store for each part and sends a kanban back upstream when something is taken. A FIFO lane has no card; its maximum is the signal. Roser's rule of thumb is to use a FIFO unless lot sizes differ between the processes, flow splits or merges, the processes are far apart or cycle times are very different.

How is this different from the kanban sizing calculator?

The kanban sizing calculator counts cards for a supermarket loop from daily demand, replenishment lead time and a safety factor. This sheet sizes a lane that has no cards, from the stop it has to cover, and adds length, refill and wait checks. The future state VSM worksheet decides where a lane goes; this sheet sizes it.

Why does the sheet check the refill time?

A lane refills only at the upstream's spare rate, its running rate minus the downstream use rate. If the press makes 257 an hour against 250 used, 83 units take 700 minutes to come back, so a stop every 240 minutes leaves the lane short. A bigger lane would not fix that; more upstream capacity or shorter stops would.

Free template

Updated October 14, 2026

FIFO lane sizing sheet

A FIFO lane sizing sheet works out how many units a first-in, first-out lane between two processes may hold before the process feeding it must stop. A FIFO lane keeps parts in the order they arrive and has a set maximum; when the lane is full, the upstream process stops until the downstream one takes a unit out. This sheet sets that maximum from the longest changeover or breakdown the lane should ride through, rounds it up to whole containers, and checks that the lane fits the floor, refills before the next stop and does not hold parts too long. The Excel version does eight lanes at once and writes the stop rule to post at each one.

Free to use: print it, copy it and edit it for your team. Enter your name and work email once to download.

Page 1 of the FIFO lane sizing sheet — Maximum in the laneWhole containersStop to coverLow markLength neededRefill timeWait when fullStop rule to postWorked example

When to use it

When to use a FIFO lane sizing sheet

When two processes sit side by side and you want a pull link between them without kanban cards.
When a lane already exists but nobody can say why its maximum is 20 or 40 units.
When a lane is always full or always empty and you need to know whether the size or the process is wrong.
When a future state map puts a FIFO lane between two steps and the team has to mark its maximum on the floor.

How to fill it in

1
Choose the lane
Two adjacent processes, one customer for the lane and parts that must keep their order. If lot sizes differ, flow splits or merges or the processes are far apart, a supermarket usually fits better.
2
Enter demand and time
Downstream demand per day and the minutes the downstream process runs after breaks. Then the upstream cycle time in seconds per unit and how many stations run in parallel.
3
Choose the stop to cover
From your downtime and changeover records, the longest changeover and the longest breakdown you want the lane to ride through. Take what a normal month shows, not the worst day of the year.
4
Read the maximum
Units used during the stop plus your margin, divided by units per container and rounded up to whole containers, never fewer than one. That number is the stop number for the lane.
5
Run the checks
Does the lane fit the length available, can the upstream refill it before the next stop, and is the wait when it is full inside any limit such as a cure time. A flag is a design problem, not always a reason for a bigger lane.
6
Mark the lane and post the rule
Paint the lane, mark the maximum and a low mark, and post the stop rule where the upstream operator sees it. After a few weeks, a lane that is always full points downstream and one that is always empty points upstream.

A filled-in example

Illustrative, not a benchmark

An example: three lanes (illustrative numbers).

Weld to paint: 480 a day over 450 minutes is 64 an hour. The 40 minute breakdown governs: 64 × 40 ÷ 60 = 42.67 units, 46.93 with a 10% margin, so 3 containers of 20 = 60 units. Length 3 × (600 + 100) = 2,100 against 2,400 available. The weld cell runs 90 an hour, so it refills the 42.67 used in 98.5 minutes against 450 between stops.
Mill to wash: 1,200 a day over 900 minutes is 80 an hour. A 30 minute changeover needs 44 units with margin, so 5 containers of 10 = 50 units, 2,250 long. Only 1,800 is free, which holds 4 containers: 40 units cover 27.3 of the 30 minutes.
Press to assembly: 2,000 a day over 480 minutes is 250 an hour. A 20 minute stop needs 91.67 units, so 2 containers of 50 = 100 units. But the press makes 257.1 an hour, only 7.1 above demand, so refilling the 83.3 units used takes 700 minutes and the stop returns every 240.

Lane 1 passes all four checks with a stop number of 60. Lane 2 is one container short of its space. Lane 3 cannot refill between stops: more upstream capacity or shorter stops will fix it, and a bigger lane would make it worse.

Common mistakes

Copying a lane size from another line
A lane of 20 that works elsewhere says nothing about your stops or your demand. Size from the stop you want covered.
Enlarging the lane to hide a slow upstream
A lane refills only at the upstream's spare rate. If the process before it is barely faster than demand, a bigger lane takes longer to refill and holds more stock.
Letting the maximum drift
A lane with no marked maximum, or one that people stack past, is a push queue. The line has to mean stop, and the upstream operator has to know it.
Using a lane where a supermarket belongs
Different lot sizes between the processes, a flow that splits or merges, or long distances make a single lane awkward. Roser's rule of thumb is to use a FIFO unless there is a reason for a supermarket.
Never checking the order
The point is first in, first out. Check now and then that units leave from the end they should, especially where order matters for traceability.

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