Demurrage vs detention
Both are daily charges the ocean carrier bills when its container is held longer than the free time you agreed. The only real difference is where the box is when the clock is running: demurrage runs inside the terminal, detention runs outside it.
Behind the terminal gate → demurrage. On your yard, your truck or your warehouse → detention.
What is demurrage?
Demurrage is charged when a full container stays inside the terminal past its free time. On imports the clock usually starts when the container is discharged and made available for collection, and stops when it leaves the gate. On exports the mirror charge applies when you deliver a full box to the terminal earlier than the receiving window allows. It is billed per container per day, and almost every carrier tariff uses rising bands so the cost accelerates the longer the box sits.
What is detention?
Detention is charged for the time you keep the carrier’s equipment outside the terminal. The clock typically starts when the container leaves the gate and stops when the empty is returned to the nominated depot. Common causes are slow unloading at the consignee, no available empty-return appointment, or a chassis shortage — and the last two are frequently not the shipper’s fault, which is exactly why detention lines are so often disputable.
Side-by-side
| Demurrage | Detention | |
|---|---|---|
| Where the container is | Inside the terminal, behind the gate | Outside the terminal, in your possession |
| What the clock measures | Days the full box sits at the port past free time | Days between gate-out and returning the empty |
| Who usually causes it | Customs holds, missing paperwork, terminal congestion, no trucking capacity | Slow unloading at the warehouse, no empty-return slot, chassis shortage |
| How it is billed | Per container per day, rising tiers | Per container per day, rising tiers |
| Common export mirror | Early arrival of a full export box before the receiving window opens | Holding an empty export box too long before returning it loaded |
How free time works
Free time is the number of days included before charges begin. It is set in your service contract or the carrier’s filed tariff, and it differs by port, equipment type and trade lane — a reefer or an out-of-gauge flat rack usually gets far less free time than a standard dry box. Two details cause most billing arguments:
- Calendar days vs working days — whether weekends and public holidays consume free time.
- The start event — discharge, availability notice, or gate-open. A one-day shift can move several days of charges.
How to calculate demurrage and detention
Subtract free days from the total days held, split the remaining chargeable days across the tariff bands, then multiply by the number of containers. The calculator below does it for you — replace the default rates with your carrier’s tariff.
Free demurrage & detention calculator
Enter your free time, the days used and your carrier’s tariff bands. Nothing is uploaded — the maths runs in your browser.
| Band | Days | Cost |
|---|---|---|
| Days 1–5 past free time | 5 | $750 |
| Days 6–10 | 4 | $1,000 |
| Day 11 onward | 0 | $0 |
Indicative only. Real invoices vary by carrier, equipment type, port and whether the tariff counts calendar or working days.
Check whether these charges are recoverable →When these charges can be disputed
A large share of demurrage and detention invoices contain at least one line that does not survive a check against the contract and the port record. The most common grounds:
- Free time counted from the wrong date — discharge, gate-open or availability was later than the carrier claims.
- Weekends and public holidays billed as chargeable days when the tariff counts working days.
- The delay was caused by the carrier or the terminal: late discharge, no empty-return appointment, equipment shortage.
- The rate applied does not match your service contract or the filed tariff for that port.
- The same days billed twice across a demurrage line and a detention line (merchant haulage splits).
- Charges continued after the container was actually returned, per the terminal record.
Carriers apply time bars, so a disputable line becomes unrecoverable if it is left too long. If your invoices are more than a few weeks old, check them before the window closes.
Want to know which of your charges are actually recoverable?
Send twelve months of carrier invoices. We check every line against your contract, the tariff and the port record, and give you a written recovery figure within 48 hours. The audit is free — our fee is 20% of what we recover, and nothing if we recover nothing.