How much detention is due on this container?

Formula, assumptions, and limits

A detention charge is the number of days charged in each band of the tariff, times that band’s daily rate, summed and multiplied by the number of containers. The days charged start the day after the last free day and end on the day the container is returned. Free time is counted from the day the container leaves the terminal, and in US tariffs it counts working days only, so a weekend inside the free time moves the last free day later.

Formula

• $C$: the charge, in the tariff’s currency.
• $N$: containers on the same dates and the same tariff.
• $t_0$: the day the clock starts, the day of interchange (gate-out full at import), counted as free day 1.
• $t_1$: the day the empty container is gated in, charged in full.
• $F$: free days, day 1 included; the last free day $t_{LFD}$ is the $F$-th counted day from $t_0$.
• $D$: calendar days charged after the last free day.
• $b_1$, $b_2$: the lengths of the first two charged bands in days; the third band runs to the return.
• $r_i$: the daily rate in band $i$, per container.

Derivation

The method is the tariff’s own table read row by row. Hapag-Lloyd’s USA Detention tariff of 1 October 2025 prints free time as “DOI+4WD”, the day of interchange plus four working days, then a “1st Period” of 3 calendar days, a “2nd Period” of 3 calendar days and “Thereafter”. Each day is priced at the rate of the period it falls in; neither the Hapag-Lloyd nor the Maersk tables reprices earlier days at a later band’s rate. Maersk numbers its bands from the start of the clock (“Day 1 to 4 Free”, “Day 5 to 8”), which is the same arithmetic with the band lengths read off as 4, 4 and the rest.

Assumptions

• Day 1 of the clock is a free day whatever the weekday, as “DOI” in the Hapag-Lloyd tariff and “commences on the day equipment departs” on Maersk’s US page.
• After day 1, free time counts only the working days chosen (Monday to Friday, Monday to Saturday, or every day). Each closed day entered adds one counted day, the rule in section G of Hapag-Lloyd’s May 2026 guide.
• Days after the last free day are charged as calendar days, weekends and holidays included, up to and including the return day.
• The same rate applies to every container in the count.

Worked example

A 40 ft dry container leaves the terminal under Hapag-Lloyd import merchant haulage, outside California, on Monday 2 March 2026 and is returned on Tuesday 24 March 2026. Five such containers moved together.

1. Free time is the day of interchange plus 4 working days: Monday 2, then Tuesday 3 to Friday 6 March. The last free day is Friday 6 March.
2. Days charged: Saturday 7 to Tuesday 24 March, 18 calendar days.
3. 1st period: 3 days × USD 200 = USD 600.
4. 2nd period: 3 days × USD 250 = USD 750.
5. Thereafter: 12 days × USD 300 = USD 3,600.
6. Per container USD 4,950; for 5 containers USD 24,750.

The same box out on Thursday 5 March has its last free day on Wednesday 11 March, because Saturday 7 and Sunday 8 are not working days. Counting calendar days instead puts the last free day on Monday 9 March and with the return still on 24 March, overcharges 2 days at the top rate, USD 600 a box.

Edge cases and limits

A container returned on or before the last free day costs nothing: with the 2 March gate-out, a return on Friday 6 March is USD 0 and on Saturday 7 March USD 200. A return date before the gate-out date is refused. The calculator draws at most 16 weeks of the calendar; longer stays are counted in full and the drawing says which weeks it shows.

Hapag-Lloyd’s California tables charge per working day, not per calendar day, and Maersk’s Philadelphia reefer and meat tables have their own bands. Neither is a preset here: enter them as your own tariff, and count the charged days by hand where they are working days.

Regulatory basis

No regulation sets the rates; the carrier’s tariff or the service contract does. In the United States the Federal Maritime Commission regulates the billing: 46 CFR Part 541, in force since 28 May 2024 under the Ocean Shipping Reform Act of 2022, sets the invoice contents and the 30-day deadlines, and 46 CFR 545.5, the 2020 interpretive rule, sets how the Commission judges whether a practice is reasonable.

Common errors

• Counting free time in calendar days when the tariff says working days, which ends free time early after any weekend.
• Leaving the day of interchange out of the free time, or counting it twice, so every band starts a day off.
• Reading Maersk’s “Day 5 to 8” as the fifth to eighth day after free time, when it is the fifth to eighth day of the clock.
• Pricing every charged day at the top band’s rate.
• Using today’s tariff for an old move: Maersk applies the free time and rates in force on the origin price calculation date.

Published detention tariffs compared

The calculator’s three preset tariffs are Hapag-Lloyd’s USA import merchant-haulage table of 1 October 2025, Maersk’s US Import Detention tariff of 20 June 2026 and Maersk’s South China combined demurrage and detention table of 1 June 2025, as each carrier publishes them. A rate is per container per day; “free” days include day 1.

Both US tariffs charge one rate for every size of dry box; only the South China table prices a 40 ft box above a 20 ft one, at RMB 350 against RMB 200 in the first band.

Maersk’s South China rates in the table are combined demurrage and detention: one clock runs from the discharge day to the day the empty is gated in, so the free days are spent in the terminal and outside it alike.

Demurrage, detention, per diem and port storage

The carriers draw the line by where the container is. Maersk’s US import page charges demurrage for “use of the land and equipment” at the port or container yard beyond free time, and detention for “the use of the equipment beyond allowed free time”, once the box has left. Port storage is a terminal’s own charge, billed separately in Maersk’s South China tariff, and some carriers call the outside charge per diem.

US regulation does not split them. 46 CFR 541.3 defines “demurrage or detention” as one term: any charge, “including per diem”, for the use of terminal space or of shipping containers, freight excluded. A carrier’s labels therefore do not change which billing rules apply in the US.

Container demurrage is a different charge from the demurrage on a voyage charter, which pays the shipowner for the ship’s time once laytime has run out; the laytime and demurrage calculator works that one out.

What a US detention invoice must show

46 CFR 541.6 lists the minimum contents, and 541.5 says an invoice missing any of it need not be paid:

• The bill of lading and container numbers, for imports the port of discharge, and the basis on which the billed party is the right party to pay.
• The invoice date and due date; the free time in days with its start and end dates; the container availability date for imports or the earliest return date for exports; and the dates charged.
• The total, the tariff rule or service contract section behind the daily rate, and the rate itself.
• A contact for mitigation, refund or waiver requests, a URL or QR code for the documents needed, and the dispute timeframes.
• Two certifications: that the charges comply with the Commission’s rules, 545.5 included, and that the billing party’s own performance did not cause or contribute to them.

The invoice must be issued within 30 calendar days of the date the charge was last incurred (541.7(a)), and the billed party gets at least 30 calendar days from the invoice date to dispute it (541.8(a)). Maersk’s US page allows 60 days from the invoice date. The rule on who may be billed, 541.4, was set aside by the D.C. Circuit in World Shipping Council v. FMC and removed with effect from 29 December 2025 (90 FR 60579); the rest of Part 541 stands.

Where to find each input

The gate-out date is on the terminal’s interchange receipt (the equipment interchange receipt) or the trucker’s gate ticket, and the return date on the gate-in receipt of the depot the carrier named. The free days and bands come from the service contract where one covers the shipment; otherwise from the carrier’s detention tariff for the country and the move type, merchant or carrier haulage. Hapag-Lloyd publishes a separate table for each. A US invoice must print the free time and the dates charged under 541.6(b), so a figure on the invoice can be checked against the one here line by line.