Glossary

Demurrage & detention

Two different clocks, one painful invoice. These per-day charges are where a fuzzy ETA stops being an inconvenience and starts being money.

In one sentence

Demurrage is the fee charged when your container stays inside the terminal beyond its free time; detention (per diem) is charged when you keep the carrier's container outside the terminal — say, at your warehouse — beyond its free time.

The two clocks

  • Demurrage clock — inside the terminal. It typically starts when the container is discharged from the vessel. You get a few "free days" (commonly 3–7, per your carrier contract and port); after that, the terminal/carrier charges per container per day, often on an escalating scale.
  • Detention clock — outside the terminal. It starts when you pick the box up. Unpack and return the empty within the free days, or pay per day until you do.

The rates escalate fast — first tier maybe tens of dollars a day, later tiers into the hundreds — and a handful of boxes stuck over a long weekend can quietly become a four-figure line item.

Why this is really an ETA problem

Almost every avoidable D&D dollar traces back to a planning miss: trucking booked for the wrong day, a chassis that wasn't there, customs paperwork started too late — all downstream of not knowing, with confidence, when the container would actually discharge. The free-time clock doesn't care what the carrier's ETA said three weeks ago. It starts when the box hits the ground.

How importers keep the clocks quiet

  • Plan pickup against a measured arrival, not the booking-confirmation date — and re-plan when the projection moves.
  • Know your port's typical dwell: how long discharge-to-available actually takes there, so free days aren't burned by terminal processing you didn't budget for.
  • Pre-clear customs and pre-book drayage against the arrival window, with a trigger to adjust when the window shifts.
  • Watch for rollovers and transshipment slips — a box arriving on a different vessel than planned is how pickups get scheduled against the wrong day entirely.

How Calibrate Freight helps you beat the clocks

Calibrate Freight gives you an arrival picture you can schedule money against: a projected ETA badged with its source and a confidence score, arriving/arrived alerts as the vessel actually closes in, and per-port dwell intelligence — median discharge dwell drawn from real historical vessel data — so you know whether "arrived Tuesday" means "truckable Tuesday" at that terminal. When the projection moves, you hear about it while there's still time to move the truck.

FAQ

What's the difference between demurrage and detention?
Location of the container. Demurrage: the full box is still inside the terminal past its free time. Detention (per diem): you've taken the carrier's container out of the terminal and kept it past its free time before returning the empty. It's possible to pay both on the same shipment — a late pickup followed by a slow unload.
How many free days do I get?
It's contractual, not universal — commonly around 3–7 days for demurrage and similar for detention, but it varies by carrier, port, equipment type, and what you negotiated. The number that matters is the one in your carrier agreement; treat defaults as worst-case.
Can demurrage be avoided entirely?
Not always — port congestion, customs holds, or chassis shortages can burn free time through no fault of yours. What's avoidable is the self-inflicted kind: pickups planned against stale ETAs. Measured arrival tracking plus realistic port dwell expectations removes most of that category.

Related terms

AISThe radio broadcast every tracker is built on — how it works, and where its coverage gaps come from. Gone darkWhen the AIS signal stops mid-ocean — what it usually means, and what an honest tracker should do about it. TransshipmentYour box quietly changes ships at a hub port — and the vessel you're watching arrives without it. RolloverBooked on one sailing, loaded on a later one — why it happens and how to catch it before the ETA lies to you.
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