Laytime

How to calculate laytime and demurrage

Published 8 August 2026 · updated 17 October 2026

Laytime is the time the charterer is allowed for loading and discharging the cargo. Demurrage is the money the charterer pays when they take longer than that. The sum itself is four numbers in a fixed order. Claims almost never depend on the sum. They depend on how the time was counted, so most of this page is about the counting.

Allowed − Used

A positive result is despatch, a negative result is demurrage. Multiply it by the daily rate, and pay part days in proportion. The hard part is never the sum. It is the time periods behind it.

This site has a free laytime and demurrage calculator. It does the sums below, including the worked example further down. You do not need an account, and nothing you type into it leaves your browser.

The calculation, in four steps:

Turn the charterparty rate into allowed time
Start the clock: notice of readiness, plus any turn time
Count the time used, minus the excepted periods
Take allowed minus used, and multiply by the daily rate

Each step has its own section below. A real claim can go wrong at any of these steps.

Step 1: how much laytime was allowed

The charterparty (the contract between ship owner and charterer) gives allowed laytime as either a period of time or a loading rate. You must turn a rate into a period before you can do anything else. Four forms cover almost every dry cargo fixture (a fixture is an agreed charter deal):

A fixed period. For example, four weather working days or six running days. There is nothing to calculate, because the period is the allowance.
A rate per day. For example, 6,000 tonnes per weather working day. Divide the quantity by the rate to get the allowance in days.
A rate per hatch per day. Two different clauses use similar words. Per working hatch per day divides by the number of hatches actually being worked. Per workable hatch per day uses the quantity in the largest hold and the daily rate for one hatch. So if the cargo is spread unevenly between holds, laytime gets longer, even when other hatches are not being used. The difference is worth money. It is decided when the deal is made, not at the berth.
No fixed laytime at all. Customary quick despatch means the charterer must work at the normal speed of the port. It sets no allowance, so there is no fixed limit to pass and no demurrage in the normal sense. As fast as the vessel can receive or deliver links the allowance to what the ship itself can handle, not to a stated tonnage.

Use the quantity actually loaded in that division. Take it from the bill of lading (the receipt for the cargo), not from the quantity written in the charterparty. Take a cargo described as 30,000 tonnes with a ten per cent option in the owner's favour. The difference between the contract figure and the loaded figure is most of a day of laytime at a typical rate. This is the most common mistake people make in their first calculation.

Load and discharge time are counted separately. The exception is when the fixture says reversible or gives one total laytime. Then the two become one shared amount, and time saved at the load port can be used at the discharge port. Reversible laytime helps the charterer, and the charterer has to negotiate for it, so the contract says so when it applies. Reversible laytime counts one voyage both ways.

Step 2: when the clock starts

Laytime does not start when the ship arrives. It does not start when work starts either. It starts when a valid notice of readiness has been given and the notice time in the charterparty has run out. That notice time is often six or twelve hours. It is called notice time or turn time. Some fixtures instead give the charterer until a set hour of the next working day.

Two kinds of clause decide whether the notice can be given at all. Under a berth charter, the ship only counts as arrived when it is at the berth, so the owner carries the risk of waiting in a busy port. Under a port charter, the ship counts as arrived when it reaches the port, so the charterer carries the waiting. WIBON (whether in berth or not) and WIPON (whether in port or not) are short terms that move that risk between the parties. They move it further than many people expect.

A notice given before the ship was really ready is not just early. On many contract forms it is invalid, and an invalid notice starts nothing. An owner can then find out months later that the clock they were billing against never started.

Step 3: what stops the clock

After laytime starts, the time used is a sum of time periods. Each period either counts or does not. The exceptions written into the fixture decide this. They are written as short codes:

Term	What it does to the count
WWD, weather working day	A day when the weather allows work. Time lost to bad weather is taken out. Contract forms differ on whether the whole stoppage or a share of the day is taken out. See weather working day.
SHEX, Sundays and holidays excepted	These periods do not count. The contract also sets their start and end. From 1700 Saturday to 0800 Monday is common, and it is not the same as midnight to midnight.
SHINC, Sundays and holidays included	These periods count. This is normal at many discharge ports and unusual at load ports.
EIU, even if used	The excepted period stays excepted even if cargo was actually worked during it. The Laytime Definitions 2013 read a bare exception the same way, so EIU mainly removes doubt. SHINC vs SHEX works one timeline under each term.
UU, unless used	The opposite: if work happens during the excepted period, that time counts.
FHEX, Fridays and holidays excepted	The same rule, for ports where the weekly rest day is Friday.
Shifting, from anchorage to berth or berth to berth	Excluded only if a clause says so, never automatically. If nobody recorded the move, the clause cannot be applied at all.
Breakdown	If the ship's own equipment breaks, that is usually the owner's risk and the time comes out. If shore equipment breaks, that is usually the terminal's risk and the time stays in. The reason written next to the stoppage decides which.

Once on demurrage, always on demurrage. The usual rule is that once laytime has run out, the exceptions stop applying. So rain stopped laytime on Tuesday, but the same rain on Thursday, after laytime has run out, is paid for as demurrage. Whether this rule applies depends on the contract wording. It is the most common point where an owner's calculation and a charterer's calculation disagree. It also means the exact moment laytime ran out is the most important time in the whole file.

Step 4: the difference, priced

Demurrage is paid at a daily rate agreed in the fixture, and part days are paid in proportion. That is why every minute has a price, and why a statement of facts (SOF) rounded to the hour can be challenged. Despatch is money the owner pays the charterer for finishing early, where the fixture allows it. By custom it is half the demurrage rate. It is paid on one of two bases, and they give different results:

All time saved. Every hour between completion and the moment laytime would have run out, including excepted periods.
Working time saved. Only the hours that would have counted as laytime. The excepted periods are taken out again.

If a Sunday falls inside the saved period, the two bases give clearly different figures from the same timeline. The basis is one line in the recap (the written summary of the deal), so read it carefully. Despatch vs demurrage prices both bases from one port call.

A worked calculation

This example has reversible laytime, one load port and one discharge port, and the ship goes onto demurrage at the second port. Every time on the left comes from the statements of facts.

CHARTERPARTY
  Cargo             30,000 mt, 10 pct more or less in owner's option
  Load rate         6,000 mt per weather working day, SHEX EIU
  Discharge rate    8,000 mt per weather working day, SHINC
  Laytime           reversible
  Demurrage         USD 14,500 per day pro rata
  Notice time       12 hours at each port

ALLOWED
  Bill of lading quantity                        31,800 mt
  Load       31,800 / 6,000 = 5.300 days        5d 07h 12m
  Discharge  31,800 / 8,000 = 3.975 days        3d 23h 24m
  Total allowed, reversible                     9d 06h 36m

LOAD PORT
  NOR tendered                       03 Aug 0800
  Laytime commenced                  03 Aug 2000
  Completed loading                  09 Aug 1400
  Elapsed                                       5d 18h 00m
  Less Sunday 09 Aug 0000 to 1400, SHEX EIU         14h 00m
  Less rain 05 Aug 0230 to 0810                      5h 40m
  Used at load                                  4d 22h 20m

DISCHARGE PORT
  Laytime remaining on arrival                  4d 08h 16m
  NOR tendered                       24 Aug 0600
  Laytime recommenced                24 Aug 1800
  Laytime expired                    29 Aug 0216
  Completed discharge                31 Aug 1000

RESULT
  On demurrage, 29 Aug 0216 to 31 Aug 1000      2d 07h 44m
  2.3222 days at USD 14,500 per day          USD 33,672.22

Three points in this example matter. First, the allowance used 31,800 tonnes, not 30,000. That adds nearly nine hours of laytime. Second, the Sunday was taken out even though the ship worked through it, because the fixture said EIU. Third, nothing was taken out at the discharge port after 29 August 0216. By then the ship was on demurrage, and the exceptions had stopped applying.

Where claims are actually lost

The statement of facts is the evidence

Every claim is decided on the statement of facts. This is a timed list of events from arrival to completion. The calculation adds up the time between those events. If the events are not recorded properly, you cannot defend the calculation, even if the sums are correct.

An interval counts only where the event that opened it counts

This rule is what makes stoppages work. A period of rain that stops laytime is recorded as an event, and the time it starts is excluded. The stoppage is never deleted from the record. Deleting it makes the timeline impossible to check, at exactly the point someone will argue about later.

A stoppage with no reason against it is a gap, not an exclusion

The same forty minutes can be bad weather, a broken shore crane or the ship's own broken equipment. It depends only on the words written next to it, and each of those three sends the money to a different party. The person who writes the claim will treat an unexplained period in their own favour, and they are entitled to do so.

Time zones

Record every event in UTC and label it as UTC. A thirty-minute time difference can move a notice of readiness before or after the exact minute the money depends on. A system that shows times in an unnamed local zone will do this without warning. Ports change to summer time on their own dates, and ships change their clocks during the voyage. So a document that says 0930 without saying which time zone cannot be checked against a notice given from a different clock.

The time bar ends more claims than the arithmetic

Most voyage charters have a time bar. A demurrage claim fails unless it is sent within a set period after discharge is completed, often ninety days. The supporting documents must go with it: the statements of facts, the notices of readiness, the bills of lading, and the pumping or time logs. A claim that arrives on day ninety-one fails. So does a claim that arrives on time without its documents. In both cases, nobody checks whether the claim was correct.

This is a filing problem, not a legal one. It is why the paperwork must stay attached to the fixture, not to the person who handled the voyage. The people who recorded the events have moved to other ships or other jobs. The claim reaches a desk where nobody was involved at the time. This is also where a desk that runs on a mail folder and a spreadsheet starts to lose money it had already earned, because claims miss the deadline or lack documents. The argument is set out in ship broker software vs spreadsheets.

The calculator above is free to use on this site and needs no account. Inside the product, the same sheet is built from the agent's signed statement of facts instead of being typed in again by hand. Retyping is where most of the counting errors on this page happen: laytime and demurrage on a working desk.

References

BIMCO, CMI, FONASBA and the Baltic Exchange, Laytime Definitions for Charter Parties 2013, 2013. fonasba.com
West of England P&I Club, Interruptions and exceptions to laytime in a nutshell. westpandi.com
Steamship Mutual, Demurrage time bars, FAQs. steamshipmutual.com
Skuld, Timebar for demurrage claims, 2015. skuld.com
BIMCO, GENCON 2022, 2022. bimco.org

The statement of factsThe agent’s timed record of everything that happened in port. Every demurrage claim is decided on it, long after anyone was there to see. Notice of readinessThe one page that starts the laytime clock: arrived, ready, tendered, and the different way each of those three is challenged. SHINC vs SHEX in laytimeWhether Sundays and holidays count against the charterer, what UU and EIU do to a worked weekend, and one timeline run under each term. Reversible laytime, with a worked exampleOne voyage counted twice, once with separate laytime at each port and once reversible, and where the difference in money comes from. Despatch vs demurrage, with a worked calculationWho pays whom when a ship finishes late or early, and one port call priced three ways from the same statement of facts. Demurrage vs detentionOne is a daily rate agreed before the delay, the other is a loss proved after it. Container shipping uses both words for something else.

Neptune Atlas

Neptune Atlas works out the time used from the statement of facts events recorded against a fixture. Each event has a UTC time with the local offset kept, and each stoppage keeps its reason instead of being removed. The demurrage or despatch figure then comes from the timeline, not from a spreadsheet. You enter the allowed laytime for each leg yourself. The rate, the exceptions and the quantity behind it come from the charterparty, so the software does not guess them. Every paid plan starts with 7 free days. A card is needed to start them, and cancelling before they end costs nothing.

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