Storage Calculator

What Is a Storage Calculator?

A storage calculator estimates detention and demurrage (D&D) storage fees based on how long a container stays at a port or terminal beyond the allotted free time. It helps shippers, freight forwarders, and carriers understand that Maritime AI™ can predict costs by factoring in daily rates, free days, and storage policies. 

Automation streamlines logistics planning, prevents unexpected charges, and optimizes container movement efficiency.

What Are Detention and Demurrage? 

Detention and demurrage are fees that are assessed after a container reaches the port. 

• Detention: a fee charged when a container is kept outside the port or terminal beyond the allowed free days before being returned
• Demurrage: a fee applied when a container remains at the port or terminal beyond the free period, before being picked up
  

Detention applies to containers outside the terminal, while demurrage applies to containers that are still within the terminal. 

How Are Detention Fees Calculated? 

Detention calculations are based on the number of days a container is kept beyond the free period, multiplied by the daily detention rate set by the shipping line. The formula is:

Detention Fee = (total days – free days) × daily detention rate

For example, a shipping company imports electronics from Shanghai, China, to the Port of Los Angeles. The container arrives at the port on March 1 and the shipper has five free days to return it, meaning they must return the empty container by March 6 to avoid detention charges.

However, due to unexpected warehouse delays, the container isn’t returned until March 9, three days past the deadline. The carrier charges a detention rate of $50 per day, so the shipper pays a detention fee of $150. This can be calculated using the detention fee formula:

(8 – 5) × $50 = $150 detention fee

How Are Demurrage Fees Calculated? 

Demurrage calculation is based on the number of days a container remains at the port beyond the free period, multiplied by the daily demurrage rate set by the shipping line. The formula is:

Demurrage Fee = (total days – free days) × daily demurrage rate

For example, a shipping company imports furniture from Shenzhen, China, to the Port of New York. The container arrives on April 10 and the shipper has four free days to pick it up, meaning it must be collected by April 14 to avoid demurrage charges.

But customs clearance takes longer than expected and the shipper doesn’t retrieve the container until April 18, four days late. The carrier charges a demurrage rate of $75 per day, so the shipper pays a demurrage fee of $300.

(8 – 4) × $75 = $300 for the demurrage fee. 

Are Detention and Demurrage Fees Significant? 

Detention and demurrage fees have been a significant financial concern for shippers in recent years. Following the global disruptions caused by the COVID-19 pandemic, supply chain bottlenecks, and port congestion led to sharp increases in these charges. In 2022, global average detention and demurrage fees rose by 12% compared to pre-pandemic levels. ​

In 2023, although global detention and demurrage fees dropped by 25%, U.S. ports still ranked among the most expensive worldwide. At major U.S. ports, average charges were $2,008 per container per day. 

These figures highlight the significant financial burden these fees place on shippers, reinforcing the need for efficient logistics planning and timely cargo movement to reduce avoidable costs.

How Does Automated Calculation Benefit Shippers?

A storage calculator helps shippers understand how an automated AI solution could help them estimate and manage detention, demurrage, and container storage fees, preventing unexpected costs and improving logistics efficiency, without the need for manual work or equations. 

Real-World Example: How a Storage Calculator Helps a Shipper

A U.S.-based furniture importer is expecting a container from Shenzhen, China, arriving at the Port of Long Beach on May 1. The shipper has five free days to pick up the container before demurrage fees apply. But their warehouse is full, and they are unsure if they can move the cargo in time.

Using a storage calculator, the shipper inputs:

• Arrival Date: May 1
• Free Days: 5 (May 1–May 5)
• Daily Demurrage Fee: $150
• Expected Pickup Date: May 8 (3 days late)
  

The storage calculator estimates a $450 demurrage fee (3 × $150). Knowing this in advance, the shipper is able to secure extra warehouse space and hire additional trucks, ensuring the container is picked up on May 5, avoiding unnecessary costs.

How Does the Windward Storage Calculator Work?

The Windward storage calculator shows how it is possible to simplify detention and demurrage management via Maritime AI™ by automating what can otherwise be a tedious and error-prone process. While calculating fees manually once or twice isn’t difficult, doing so at scale, across dozens or hundreds of containers moving through different ports with varying terms, can quickly become overwhelming. 

Shippers simply input shipment details and select container dates to receive real-time, accurate fee estimates. Full automation, as demonstrated via the container calculator, eliminates the need for manual spreadsheets, reduces errors, and ensures nothing falls through the cracks. By leveraging AI-powered insights, our container calculator enhances decision-making, boosts efficiency, and helps stakeholders avoid costly surprises.