What Is Throughput in Manufacturing? How Throughput Works

Throughput is an efficiency measure in manufacturing. It measures the rate at which your operation produces sellable, finished goods over time. 

Tracking throughput helps businesses gauge whether production is working as it should. But on its own, a throughput number can suggest production is fine when output is falling behind.

This guide explains what throughput in manufacturing is, how to calculate it with a simple formula, and how it differs from similar metrics. It also covers the most common constraints on throughput and the practical ways to raise it.

What is throughput in manufacturing?

Throughput in manufacturing is the rate at which a production system puts out quality, sellable units over a set period of time. Whether that system is a single machine, a workstation, a line, or a whole plant, throughput measures average output per unit of time, such as units per hour or per shift.

Only correctly made, sellable products count. Scrap and anything you send back through production for rework are not counted in throughput, even though they took time and materials to make. 

Throughput differs from throughput time, which is the time a single unit takes to travel from raw material to finished goods.

How to calculate throughput

To calculate throughput, divide the number of good units you produced by the length of the time period using this formula:

Throughput = Units produced / Time period

Units produced is the count of sellable products you complete, not including scrap and anything headed for rework. The time period is a consistent window you choose, whether that’s an hour, a shift, or a day.

For example, if a line finishes 480 good units during an eight-hour shift, its throughput is 480 divided by eight, or 60 units per hour.

Calculating throughput using Little’s Law

Another way to calculate throughput is using Little’s Law, which helps estimate throughput when you already know your work-in-process amount and the cycle time. It can be useful when your production flow is relatively stable, and you want a quick way to understand system performance.

Little’s Law defines throughput as work in process (WIP) divided by cycle time (CT). 

Throughput = Work in process / Cycle time

Work in process is the number of units currently in production, including those being worked on and waiting between steps. Cycle time is the time it takes one unit to move through the production process from start to finish. 

For example, if 240 units are in process and it takes 30 minutes to be completed, throughput is 240 divided by 30, or 8 units per minute.

Throughput vs. capacity, output, and related metrics

Throughput is a rate: The amount of sellable output a production line produces over time. It’s different from production volume, which is the total amount produced; capacity, which is the maximum output you could produce; and cycle time, which is the time it takes one unit to move through the process. Here’s a breakdown of each metric:

What affects manufacturing throughput?

Throughput almost always runs below capacity, and it does so for specific operational reasons. Common factors include:

• Bottlenecks or constraints. The slowest step in the process limits everything downstream, so the line can only move as fast as its tightest point.

• Unplanned equipment downtime. When a machine breaks down or a station runs out of material, that lost run time can lower output.

• Supply and material delays. Late supplier orders or unreliable transportation can leave the production line without the inputs it needs to produce the desired outcome.

• Quality problems and rework. Defects that lead to scrap reduce the number of finished units.

• Queue and wait time. Units waiting between steps, along with piled-up work in process, lengthen production time, holding throughput below capacity.

How to improve throughput

Improving your throughput starts with identifying and fixing any constraints, then addressing the biggest sources of lost time and defects. Speeding up any step that’s not the constraint won’t increase your overall output. 

Here are four ways to improve throughput:

• Relieve the bottleneck first. The slowest step sets the pace for the line’s output, so improve that point before other areas.

• Reduce unplanned downtime with preventive maintenance. Fewer breakdowns means more available production time and more sellable units. The US Environmental Protection Agency (EPA) reports that companies adopting total productive maintenance (a planned maintenance approach), can realize a 15% to 25% increase in equipment efficiency rates within three years. 

• Reduce changeover and setup time. The single-minute exchange of die method shortens the time it takes to switch a machine from one job to the next, which adds productive run time without adding equipment.

• Reduce defects and rework. Throughput counts only good units, so improving quality raises your sellable output. Continuous-improvement methods can help raise production line productivity and reduce recurring errors.

After any change, measure throughput again to confirm your rate actually improved.