Laytime

Reversible laytime, with a worked example

Published 12 October 2026

Reversible laytime lets the charterer add the time allowed for loading to the time allowed for discharging and use the total as one allowance. Time saved at the load port can then be spent at the discharge port. This page works one voyage both ways. The cargo, the ports and the weather are the same. Only the one word changes, and it moves 11,250 dollars.

What the word means

The Laytime Definitions for Charter Parties 2013, agreed by BIMCO, CMI, FONASBA and the Baltic Exchange, define it in definition 24:

Reversible laytime "shall mean an option given to the charterer to add together the time allowed for loading and discharging. Where the option is exercised the effect is the same as a total time being specified to cover both operations."

Three points follow from those two sentences.

It is the charterer's option. The owner cannot insist on it. If the charterparty (the charter contract) says when the option must be declared, declare it then.
It works between loading and discharging. BIMCO's commentary on the definition says reversibility applies between loading ports and discharging ports, but not between two loading ports or between two discharging ports.
The result is one clock. There is one allowance, one moment when it runs out, and one demurrage calculation for the voyage.

The Baltic Exchange glossary gives the opposite term too. Non reversible means the time allowed for loading and for discharging "cannot be computed together". Each port then has its own allowance and its own result. Laytime is non reversible unless the fixture (the agreed deal) says otherwise.

The fixture used in the example

The figures are round and made up for the arithmetic. They are not a market quote.

CHARTERPARTY
  Cargo            55,000 mt bulk, bill of lading quantity 55,000 mt
  Load rate        10,000 mt per weather working day, SHINC
  Discharge rate    8,000 mt per weather working day, SHINC
  Demurrage        USD 18,000 per day pro rata
  Despatch         half demurrage, USD 9,000 per day, on working time saved
  Notice time      12 hours at each port

ALLOWED
  Load        55,000 / 10,000 = 5.500 days        5d 12h 00m
  Discharge   55,000 /  8,000 = 6.875 days        6d 21h 00m
  Total, if reversible       12.375 days         12d 09h 00m

LOAD PORT, from the statement of facts
  NOR tendered                     01 Jun 2000
  Laytime commenced                02 Jun 0800
  Rain, work stopped               04 Jun 0100 to 0400
  Completed loading                06 Jun 1700
  Elapsed                                         4d 09h 00m
  Less rain                                           3h 00m
  Used at load                                    4d 06h 00m

DISCHARGE PORT, from the statement of facts
  NOR tendered                     19 Jun 1800
  Laytime commenced                20 Jun 0600
  Rain, work stopped               22 Jun 1000 to 1600
  Completed discharge              28 Jun 1800
  Elapsed                                         8d 12h 00m
  Less rain                                           6h 00m
  Used at discharge                               8d 06h 00m

The ship was fast at the load port and slow at the discharge port. That is the pattern where the word matters most.

Counted separately, without the word

Each port is its own calculation. The load port finishes early, so the owner pays despatch (money for time saved). The discharge port runs over, so the charterer pays demurrage (the daily charge for delay).

LOAD PORT
  Allowed                                         5d 12h 00m
  Used                                            4d 06h 00m
  Saved                                           1d 06h 00m
  Despatch   1.250 days x USD 9,000          USD 11,250.00   owner pays

DISCHARGE PORT
  Allowed                                         6d 21h 00m
  Laytime expired                  27 Jun 0900
  Completed                        28 Jun 1800
  On demurrage                                    1d 09h 00m
  Demurrage  1.375 days x USD 18,000         USD 24,750.00   charterer pays

NET                                          USD 13,500.00   to the owner

The expiry time is the start, plus the allowance, plus the six hours of rain that fell while laytime was still running: 20 June 0600, plus 6 days 21 hours, plus 6 hours.

Counted together, reversible

Now the two allowances are one. The charterer arrives at the discharge port with whatever is left of the total.

TOTAL ALLOWED                                    12d 09h 00m
  Used at load                                    4d 06h 00m
  Remaining on arrival at discharge               8d 03h 00m

DISCHARGE PORT
  Laytime recommenced              20 Jun 0600
  Laytime expired                  28 Jun 1500
  Completed                        28 Jun 1800
  On demurrage                                        3h 00m
  Demurrage  0.125 days x USD 18,000          USD 2,250.00   charterer pays

NET                                           USD 2,250.00   to the owner

Check it the other way. Total used is 4 days 6 hours plus 8 days 6 hours, which is 12 days 12 hours. Total allowed is 12 days 9 hours. The difference is 3 hours.

USD 11,250

The gap between the two answers, 13,500 against 2,250. It is exactly the time saved at the load port, 1.25 days, multiplied by the gap between the demurrage rate and the despatch rate, 9,000 dollars a day.

Where the difference comes from

The time is the same in both versions. The ship was 30 hours quick at one end and 33 hours slow at the other. What changes is the price put on the 30 hours.

Counted separately, the charterer is paid for the saved 30 hours at the despatch rate, which is half the demurrage rate. The charterer then pays for the 33 slow hours at the full rate. Counted together, the 30 saved hours cancel 30 of the slow hours directly, so they are worth the full demurrage rate. That is why reversible laytime favours the charterer, and why an owner gives it only when it has been negotiated.

The rule of thumb for the gap: time saved at the fast port, times the difference between the demurrage and despatch rates. If the fixture pays no despatch at all, the saved time is worth nothing when counted separately, and the full demurrage rate when reversible.

You can check each port with the free laytime calculator. For the reversible version, enter the remaining 8 days 3 hours as the allowance at the discharge port.

Reversible is not the same as averaging

A third wording sits between the two. Definition 23 says that to average laytime means "separate calculations are to be made for loading and discharging and that any time saved in one operation is to be set off against any excess time used in the other".

In the example, averaging gives the same 3 hours: 33 hours over, less 30 hours saved. The two methods can part company on other timelines, because they are built differently:

	Reversible	To average
Calculations	One, on the total time	Two, set off against each other at the end
When laytime runs out	Once, when the total is used up	Separately at each port
Laytime exceptions at the second port	Apply only until the total runs out	Apply until that port's own allowance runs out

The last row is where the money can differ. Exceptions such as rain and excepted Sundays normally stop applying once a ship is on demurrage. Under a reversible count, a slow load port can use up the whole allowance before the discharge port starts, so the ship arrives already on demurrage and no exception helps the charterer there. Recaps that say only "laytime reversible" or "to average" settle which method applies. Recaps that say "total laytime" with one figure have the same effect as reversible.

Four things to settle when fixing reversible

Notice time at the second port. If the ship arrives with laytime already used up, does the notice time still run before demurrage starts? Charterparties differ. Write it down.
The quantity. Both allowances use the quantity actually loaded. A cargo loaded ten per cent over the contract figure adds ten per cent to both.
More than two ports. With two load ports, say whether the load time is one allowance across both.
Despatch. There is one result for the voyage, so despatch is paid, if at all, only when the total has not been used. See despatch vs demurrage for how saved time is priced.

The full method for a single calculation, with exceptions and the time bar, is in how to calculate laytime and demurrage. This page explains how the terms are defined and normally applied. It is not legal advice, and the charterparty decides the count.

References

BIMCO, CMI, FONASBA and the Baltic Exchange, Laytime Definitions for Charter Parties 2013, with BIMCO Special Circular No. 8 commentary, 2013, definitions 23, 24, 30 and 31. fonasba.com
Baltic Exchange, Shipping Glossary, entries for reversible and non reversible, read 12 October 2026. balticexchange.com
BIMCO, GENCON 2022, 2022. bimco.org
West of England P&I Club, Interruptions and exceptions to laytime in a nutshell. westpandi.com

How to calculate laytime and demurrageWhen the clock starts, what stops it, how the demurrage figure is worked out, and why most claims fail on the paperwork, not on whether they were right. 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. Weather working day in laytimeThree wordings of the same weather exception, and what each one takes out of laytime for the same two hours of rain. 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.

Neptune Atlas

The Neptune Atlas laytime sheet holds every port of a fixture on one page and carries the time used at the load port into the discharge port when the fixture is reversible, so the expiry time at the second port is worked out from the first. The events come from the signed statements of facts, each stoppage with its reason, so the sum can be checked line by line when the claim is questioned. Every paid plan starts with 7 free days. A card is needed to start them, and cancelling before they end costs nothing.

Try 7 days free Ship chartering software for brokers What each plan includes