What it means
Every business process, from manufacturing a product to delivering a service, is made up of a chain of connected steps. Just like a physical chain is only as strong as its weakest link, the overall output of a business is limited by its most restrictive step.
This limiting factor is known as the constraint. Management guru Eliyahu Goldratt introduced this concept to help businesses stop wasting time optimising areas that are already running efficiently.
If your shipping department can process fifty orders a day, but your packing station can only handle twenty, pouring more money into shipping does nothing to increase total sales. The packing station is the constraint.
In practice, applying this framework involves five focused steps. First, identify the constraint, and second, decide how to exploit it to get the maximum possible output.
Third, subordinate everything else in the business to support this decision. Fourth, elevate the constraint by investing more resources into it if necessary.
Finally, repeat the process for the next bottleneck that appears. For non-finance managers, this means shifting focus away from local efficiencies, such as keeping every machine busy, and focusing instead on global throughput.
Making non-bottleneck processes faster just creates piles of unfinished work-in-progress, tying up cash and increasing storage costs without adding any actual value for customers. Imagine a bucket brigade putting out a fire.
Even if twenty people are passing buckets quickly at the start of the line, the amount of water reaching the fire is entirely limited by the one person who can only pour water slowly into the fire engine.
In practice
Real-world examples
Example 1
A custom furniture startup realised its woodworking artisans finished chairs faster than the final varnish team could coat them. By shifting one artisan to help with varnishing, daily output rose from 10 to 15 chairs, directly lifting revenue. The change cost nothing in new equipment.
Example 2
A mid-sized accountancy firm found that tax return delivery was stalled because only the senior partner could sign them off. Delegating preliminary reviews to managers cleared the backlog, allowing the firm to bill 30% more clients each month. The partner kept the final sign-off, so quality was protected.
Example 3
A regional bakery discovered its delivery van capacity limited daily wholesale orders. Renting an extra trailer instead of buying a new van allowed it to supply five new supermarkets, boosting weekly gross profit by $2,000. The trailer rental cost far less than a new vehicle.
Think of it
Imagine a bucket brigade putting out a fire. Even if twenty people are passing buckets quickly at the start of the line, the amount of water reaching the fire is entirely limited by the one person who can only pour water slowly into the fire engine.
Formula
Calculation
System Throughput = Minimum (Step 1 Capacity, Step 2 Capacity, Step 3 Capacity)
Worked example: a bakery mixes 100 loaves an hour, bakes 80 loaves an hour, and packages 120 loaves an hour. The total output is constrained to the minimum, which is 80 loaves an hour, and the oven is the constraint.
Now put a dollar value on it. If each loaf sells for $4 and the materials cost $1.50, each loaf earns $2.50 of throughput, so the bakery earns 80 x $2.50 = $200 an hour. Adding oven capacity to reach 90 loaves an hour lifts this to 90 x $2.50 = $225, an extra $25 an hour, or $200 over an 8-hour shift. Speeding up the mixer or packer instead adds $0.Case study
Seen in the real world
GreenLeaf Packaging, a fictional box manufacturer, struggled with low profits despite high demand. The plant manager used the Theory of Constraints to analyse the production floor. The cutting machine processed 500 units per hour, the printing press processed 200 units per hour, and the gluing machine processed 450 units per hour. The printing press was the clear bottleneck. Work-in-progress inventory piled up in front of the printers, tying up working capital.
Instead of buying a new cutting machine, management scheduled the printing press to run during lunch breaks and maintenance shifts, squeezing extra hours out of the existing asset. They also assigned an assistant to prep inks beforehand so the press operator never had to stop to fetch supplies. Output jumped from 200 to 260 units per hour, a 30% increase in sellable output without buying new machinery. The printing press is still the constraint at 260 units per hour, because that is below the 450 units per hour the gluing machine can handle. Management planned to keep raising printing capacity until it approached 450, at which point the gluing machine would become the next constraint and their focus would move there.
Watch out
Common mistakes
- Treating every department as equally important instead of focusing exclusively on the current bottleneck.
- Trying to optimise non-bottleneck steps, which wastes money and creates excess inventory.
- Failing to look for the next constraint as soon as the previous one is resolved.
Questions
People also ask
What is a bottleneck?
A bottleneck is a point in a process where work piles up because the capacity of that specific step is lower than the demand or the capacity of the steps around it.
Does this theory only apply to manufacturing?
No, it applies to any process. This includes service businesses, software development, hospital waiting rooms, and administrative workflows.
How do I know if I have found the right constraint?
The true constraint is usually the step where work-in-progress inventory piles up and the surrounding steps are waiting for work to arrive.