What is the difference between demurrage and detention?

Demurrage is charged when a full container sits inside the port or terminal beyond its free time. Detention is charged when you keep the carrier's container outside the terminal, at your warehouse, longer than the free time allowed for unpacking and return.

How is free time counted?

Free time is the number of days the carrier allows before charges start, usually counted from when the container is available or gated out. This tool subtracts the free days from the total days held, and only the excess is chargeable.

Why are there two rate tiers?

Carriers escalate per-diem rates the longer a container is held, to push faster turnaround. The first few chargeable days are billed at a lower tier-one rate and later days at a higher tier-two rate. Enter your carrier's specific thresholds.

Are weekends and holidays charged?

It depends on the carrier and port. Some count calendar days including weekends, others count working days only. This calculator treats the dates as calendar days, so adjust your inputs if your tariff excludes non-working days.

Can I use this to dispute an invoice?

Yes. Recomputing chargeable days against the granted free time and published rates is the fastest way to catch carrier billing errors, which are common. Bring your detention and demurrage tariff and the gate-in and gate-out timestamps.

Demurrage & Detention Calculator

Demurrage and detention charges escalate fast and carrier invoices often contain errors. This calculator counts only the chargeable days beyond your granted free time, applies tiered per-diem rates, and totals both charges so you can check an invoice line by line before paying it.

How it works

Held days are measured from the dates, free time is removed, and the remainder is split across two rate tiers:

held days       = return/pickup date − available date
chargeable days = max(0, held days − free days)
tier-1 days     = min(chargeable days, tier-1 window)
tier-2 days     = chargeable days − tier-1 days
charge          = tier-1 days × rate-1 + tier-2 days × rate-2

Demurrage and detention are computed independently with their own free time and rates, then summed for the total exposure.

Example and tips

A container available on day 0 and returned on day 10 with 5 free days has 5 chargeable days. With a 3-day tier-one window at 75 per day and 110 per day after, that is 3 × 75 + 2 × 110 = 445 of demurrage. Always confirm whether your tariff counts calendar or working days, because a weekend can swing the bill by hundreds and is the single most common source of an over-billed invoice.