Demurrage and detention calculator

Charges start once the free days are used up. Every day the container is kept after that is a chargeable day, and tariffs usually price those days in tiers: a daily rate for the first few days, a higher one for the next few, and a top rate for every day after. Enter each tier's length and rate as the tariff states them, and leave the last tier's length blank so it covers every remaining day.

Tariffs differ on when free time starts and on whether weekends and holidays count. This calculator counts the days exactly as you enter them, so enter calendar or working days to match the tariff that applies.

A container is kept 12 days with 4 free days, so 8 days are chargeable. If the tariff charges 100 a day for days 1 to 4 and 150 a day after that, the first four chargeable days cost 400 and the next four cost 600, for an estimated 1,000.

With free time starting on November 2 and 4 free days, the last free day is November 5. The 12 days kept here run to November 13.

Demurrage usually applies while a loaded container stays at the terminal past its free time, and detention while the container is outside the terminal and not yet returned. Some lines combine the two into one charge. The last free day is the final day before either begins.

In the United States, the Federal Maritime Commission sets what a demurrage or detention invoice must show and when it must be issued. Read the FMC's billing rules, explained, then compare the invoice's free-time dates and charged days with your own estimate.

This estimate is a planning aid. The tariff, your contract and the invoice decide what is owed.