Demurrage, detention and storage are often discussed together because all three can arise when containers stay in a process longer than expected. They are not interchangeable, and the exact terminology can vary by carrier, terminal and contract.
Demurrage: time before the container leaves the terminal
In a common import workflow, demurrage relates to the period a container remains in the terminal beyond the carrier's allowed free time. The dates that matter are usually arrival or availability, the applicable free-time rule and the terminal exit date.
Detention: time using the carrier's equipment outside the terminal
Detention commonly applies after gate-out while the container is outside the terminal. The critical date is then the empty-return date. If the equipment is returned after the allowed period, daily charges may begin.
Storage: a terminal or facility charge
Storage is generally charged for occupying terminal, depot or warehouse space. It may run alongside a carrier charge, which is why a team can occasionally face more than one type of cost for the same delayed operation.
Why “free days” are not one universal number
Free time can depend on port, carrier, equipment, contract, service and whether days are counted as calendar or working days. Some tariffs also use escalating tiers, so day 8 may cost more than day 6.
The dates worth tracking
- Arrival or availability date.
- Last free day in terminal.
- Actual terminal exit date.
- Equipment free-time allowance.
- Empty-return date.
- Daily rate or tariff tier.
Those dates make it possible to estimate exposure before an invoice arrives.
Estimate chargeable days with the free Demurrage & Free Days Calculator →
Example
If a container has five terminal free days and leaves two days after that allowance, the first exposure is two demurrage days under a simplified model. If the carrier then grants three equipment free days after gate-out and the empty unit is returned two days late, that creates a second detention exposure.
What the calculator cannot know automatically
A generic tool cannot determine your contractual tariff, exceptions, terminal rules or whether a specific date is chargeable. Always validate the estimate against the carrier or terminal conditions that apply to the shipment.
Operational control is more important than the invoice
The best time to identify exposure is before the cost becomes final. A tracker that highlights last free day, gate-out and empty return lets the operations team act while there is still time to avoid or reduce the charge.
See the Demurrage & Free Days Excel tracker →
