Inventory duration is one of the central key performance indicators in warehouse logistics. It indicates how long goods remain in storage on average, directly influencing capital commitment, storage costs, and profitability. In this article, you will learn how to calculate inventory duration, which factors influence it, and how you can make your warehouse processes more efficient with targeted measures.
Table of contents:
- What is inventory duration? Definition
- Formula for calculating inventory duration
- Calculating and optimizing average inventory duration
- How can average inventory duration be reduced?
- Improving inventory duration and leveraging synergies
What is inventory duration? – Definition
Inventory duration describes the average length of time an item remains in the warehouse before it is processed, picked, or shipped. Also known as turnover time, it is a key metric in warehouse logistics.
The general rule is: The shorter the inventory duration, the lower the capital commitment – and the more efficient the warehouse management. A low inventory duration has a positive impact on liquidity, storage costs, and overall supply chain performance.
Optimizing capital commitment
The art of proactive warehouse management lies in balancing inventory duration against various objectives. The goal is to avoid holding excessive stock that ties up unnecessary capital, as this has a direct impact on the company's liquidity. An optimized inventory duration improves liquidity.
Reduce fixed costs
There is also a positive effect on fixed costs. Optimized storage duration means that less space is required for the same warehouse performance. Construction and storage usage costs decrease. Any additional external warehouse rentals can be scaled back, thereby easing the cost burden.
Ensure product availability
On the other hand, inventory levels must not be planned too tightly during warehouse management to avoid bottlenecks or delays in supplying your own production or fulfilling customer orders. Such issues would equally harm a company's profitability.
Formula for calculating storage duration
Would you like to calculate the storage duration for your own inventory management?
A simple formula serves as the basis for this:
Average storage duration = 360 days (or 365 days) x average inventory divided by annual consumption
For logistics professionals, the storage duration of different product groups is particularly interesting. This can be calculated using the same formula and the corresponding figures.
Calculate inventory turnover rate
Another important key performance indicator is the inventory turnover rate. This figure indicates how often an average inventory level was completely removed from a warehouse and replaced during a fiscal year. Use this formula to calculate your inventory turnover rate:
Inventory turnover rate = Sales revenue / Value of average inventory
Calculate the inventory interest rate
Regarding storage duration, another logistics KPI of high relevance is the so-called inventory interest rate. This can be used to calculate the impact of warehouse optimization on a company's profitability. After all, stored goods tie up capital that cannot be put to work elsewhere for the company. Therefore, the capital tied up in inventory is hypothetically compared against the return that could have been achieved in the same period.
You can use the following formula for this:
Inventory interest rate = annual interest rate x average storage period divided by 360
Calculating and optimizing average storage period
What benchmark should companies aim for regarding their average storage period? There is no one-size-fits-all answer to this question, as it depends on various internal and external factors. The current procurement situation plays a major role. Can raw materials and goods be procured quickly and reliably at any time? Or are there supply and transport bottlenecks that make additional stockpiling advisable for security?
Furthermore, industry-specific characteristics must be taken into account: in the consumer sector, retail, and e-commerce, storage periods tend to be shorter, while manufacturing companies generally have longer storage times—if only to ensure secure production chains. It is therefore recommended to use benchmarks and best-practice examples from similar fields and your own industry to evaluate your storage period.
How can the storage period be reduced?
A short storage period means less tied-up capital, reduced storage costs, and greater flexibility. The goal of efficient warehouse management is therefore to keep the average storage period as low as possible. Four proven approaches help with this:
1. Real-time data through an inventory management system
A modern inventory management system provides transparent inventory data in real time. This enables well-founded purchasing planning, reduces safety stocks, and avoids overstocking.
2. Digitally managing warehouse processes
With smart warehouse management software like TradeLink, incoming and outgoing goods can be coordinated efficiently. The result: less downtime, faster turnover, and more transparency along the supply chain.
3. Just-in-time delivery
Just-in-time concepts minimize storage times by having materials delivered only when needed. Prerequisite: precise planning and coordination with suppliers—ideally digitally supported.
4. Optimizing production planning
In production, precise manufacturing control helps to smooth out material flows and shorten storage times. This reduces storage costs and shortens lead times.
Conclusion
Smart warehouse management and forward-looking procurement will lead to a noticeable reduction in storage periods over the long term, allowing your company to benefit from liquidity advantages. When it comes to warehouse optimization individual factors of the goods to be stored must also be taken into account. These include specific item characteristics such as expiration dates, fragility, special storage requirements, and the maximum possible storage duration.
