A bottleneck is the stage of a process that can handle the fewest items per hour. Every item has to pass through it, so it decides how much the whole process can produce. In a case question you are given a list of stages and capacities, and you pick out the limiting one.
This lesson comes after calculating productivity in operations and productivity, because a bottleneck is a common reason why productivity stays low.
How do you find the bottleneck?
The bottleneck is the stage with the lowest capacity. The process can never produce more per hour than that stage, whatever the other stages can do.
Think of a water bottle with a narrow neck. The body of the bottle may be wide, but water can only pour out as fast as the neck allows. Output of the whole process is the capacity of the narrowest stage.
Use these steps.
- List each stage with its capacity per hour.
- Find the lowest figure. That stage is the bottleneck.
- Output per hour equals that figure. Multiply by hours to get output per shift.
- Check what improvement would do. Speeding up a stage that is not the bottleneck changes nothing.
Worked example
Nasi Lemak Mak Ani runs a central kitchen that prepares packed nasi lemak. The stages and their capacities per hour are shown below.
| Stage | Capacity (packs per hour) |
|---|---|
| Prepare ingredients | 180 |
| Cook rice and sambal | 150 |
| Pack | 120 |
| Label and seal | 200 |
Step 1, find the lowest capacity. Packing at 120 packs per hour is the lowest. It is the bottleneck.
Step 2, output per shift. 120 × 8 hours = 960 packs.
Step 3, test an improvement. Each packer handles 60 packs an hour, so there are 2 packers now. The owner hires a third packer, which raises packing to 3 × 60 = 180 packs per hour.
Step 4, find the new bottleneck. The capacities are now 180, 150, 180 and 200. The lowest is cooking at 150, so cooking is the new bottleneck.
Step 5, new output. 150 × 8 = 1,200 packs. That is 1,200 − 960 = 240 more packs per shift. To go further, the kitchen would need more cooking capacity, not another packer.
The mistake to watch for
A common slip is to improve the stage that looks busiest or most visible.
Mistaken answer: “To raise output, Mak Ani should buy a faster labelling machine, because labelling is the last step before delivery.”
Labelling already handles 200 packs an hour. Speeding it up leaves output at 120 packs an hour, because packing still limits the line.
The correction is to find the lowest capacity first. Money spent anywhere else adds cost but no extra output. A good answer names the bottleneck stage, gives its capacity and explains why that figure limits everything else.
Check yourself
Try these on paper, then open each answer.
1. A workshop has four stages with capacities of 90, 75, 110 and 80 units per hour. Which is the bottleneck, and what is output in a 7-hour day?
Show answer
The lowest capacity is 75 units per hour, so that stage is the bottleneck. Output: 75 × 7 = 525 units.
2. In question 1, the 75-unit stage is doubled to 150. What is the new bottleneck and the new output per hour?
Show answer
Capacities are now 90, 150, 110 and 80. The lowest is 80, so the fourth stage becomes the bottleneck. Output rises from 75 to 80 units per hour, a gain of only 5.
3. The owner of the workshop wants to buy a faster machine for the stage that handles 110 units per hour. Explain whether this will raise output.
Show answer
It will not. That stage already has more capacity than the bottleneck. Output stays limited by the 75-unit stage, so the money would add cost without adding output.
Where this leads next
Next, look at how a firm checks its output in explaining a quality-control step, then test yourself on the operations practice set. Later, technology, quality and sustainability shows how firms try to remove bottlenecks with new equipment.
Some students find the bottleneck correctly but struggle to write a recommendation that names its limits. A teacher in online one-to-one Business tuition can help you practise exactly that.