Built for the people who live with the clock: chartering managers, operators, port agents, demurrage analysts and traders. Almost every voyage-charter dispute eventually collapses into one laytime calculation — yet the rules are split across the Laytime Definitions, decades of case law and the charter party's own clauses, and no single page puts the vocabulary, the method and the worked examples together. We assembled it here.
Every calculation in this reference can be reproduced, saved and exported in the rynda laytime & demurrage calculator — it counts laytime against your clauses and produces a defensible statement.
📖 See also: ECA / SECA zones reference · EU ETS & FuelEU cost reference
Contents
- At a glance
- The four core concepts
- The timeline of a port call
- Notice of Readiness (NOR)
- Statement of Facts (SOF)
- How laytime is counted — the clause glossary
- Worked example 1 — the clean case
- Worked example 2 — weather and exceptions
- Worked example 3 — reversible laytime
- Demurrage in practice
- Despatch and detention
- Common disputes and traps
- For developers and operators
- FAQ
- References
At a glance
The short version, if you read nothing else:
- Laytime is the time the owner sells to the charterer to load and discharge, priced into the freight. Demurrage is what the charterer pays when they use more than that. Despatch is what the owner pays back when the charterer uses less.
- The clock is armed by a valid Notice of Readiness (NOR) and evidenced by the Statement of Facts (SOF). Get the NOR wrong and the whole calculation can collapse.
- Laytime is almost never "wall-clock time." Weekends, holidays and bad weather may or may not count depending on a handful of abbreviations in the charter party (SHEX, WWD, SHINC, FHEX…). Those abbreviations are the calculation.
- "Once on demurrage, always on demurrage" — once laytime is exhausted, exceptions that used to pause the clock generally stop working. Time runs continuously, including weekends and weather, unless the CP explicitly says otherwise.
- Demurrage is a liquidated daily rate (a pre-agreed sum needing no proof of actual loss), pro-rated to the minute; despatch is customarily half the demurrage rate.
- A demurrage claim is only as good as its documents, and it is usually time-barred (often 90 days from completion of discharge) — a well-founded claim dies if filed late or without the SOF and supporting papers.
This is a practical reference, not legal advice. The charter party wording always governs; where it is silent, the Laytime Definitions and case law fill the gaps.
The four core concepts
| Term | Who pays | What it is |
|---|---|---|
| Laytime | (bought in freight) | The period allowed to the charterer for cargo operations, free of extra charge. |
| Demurrage | Charterer → Owner | Liquidated damages for detaining the ship beyond laytime. |
| Despatch | Owner → Charterer | A reward for finishing within laytime — time saved. Usually half the demurrage rate. |
| Detention | Charterer → Owner | Damages at large for delay outside the laytime/demurrage regime (e.g. after an invalid NOR, or for a cause the demurrage clause doesn't cover). |
The mental model: laytime is a budget of time. Demurrage is the overdraft fee when you blow the budget. Despatch is the rebate when you come in under. Detention is what happens when you are delayed by something the budget was never meant to cover.
The timeline of a port call
Every laytime calculation walks the same sequence. Know it cold:
- Arrival — the ship reaches the agreed destination (a berth under a berth charter, or the port / usual waiting place under a port charter). Becoming an "arrived ship" is a legal test, not just a GPS fix.
- NOR tendered — the master gives Notice of Readiness that the ship has arrived and is ready in all respects to load/discharge.
- NOR valid & accepted — the notice must be given at the right place, time and in the right form; the ship must be genuinely ready (holds, documents, free pratique — the port-health/quarantine clearance to enter — and customs).
- Turn time / notice time — a grace period after a valid NOR before laytime starts (e.g. "laytime to commence 6 hours after NOR" or "at 0800 next working day").
- Laytime commences — the clock starts.
- Laytime counts — time runs subject to the CP's counting rules (which days, which hours, weather).
- Interruptions & exceptions — periods the CP says do not count (weekends under SHEX, weather under WWD, strikes, breakdowns).
- Laytime expires — the allowed time is used up.
- On demurrage — all further time runs continuously (the "once on demurrage" rule).
- Completion — cargo operations finish; the SOF is closed and signed.
Steps 2–4 are where most money is won or lost. A defective NOR can push "laytime commences" hours or days later — or convert the whole delay into detention.
Notice of Readiness (NOR)
The NOR is the trigger. For it to arm the clock:
- The ship must be an "arrived ship." Under a berth charter, that means in the berth. Under a port charter, reaching the port / usual waiting anchorage can be enough (the classic Johanna Oldendorff "reachable on arrival" line of authority). This distinction decides whether waiting-at-anchor time counts.
- The ship must be ready in all respects — holds clean and cargo-ready, gear working, documentation and (where required) free pratique and customs clearance in place. A NOR tendered by a ship that isn't actually ready is invalid.
- It must be tendered at the right time and place, in the manner the CP prescribes (in writing, to the named receivers, within the stated hours).
The "when in" clauses
Charters use abbreviations to let a NOR be tendered before the ship is formally at berth, to protect the owner from congestion:
| Clause | Expands to | Effect |
|---|---|---|
| WIBON | Whether In Berth Or Not | NOR may be tendered even if no berth is available (congestion risk shifts to charterer). |
| WIPON | Whether In Port Or Not | NOR valid even before entering port limits. |
| WIFPON | Whether In Free Pratique Or Not | Readiness not defeated by pending pratique. |
| WICCON | Whether In Customs Clearance Or Not | Readiness not defeated by pending customs. |
These clauses are worth real money in congested ports — they can start the clock while the ship is still at anchor. Read them together with the "arrived ship" test.
Invalid NOR — the expensive trap
If the NOR is invalid (ship not truly ready, wrong place/time, no free pratique where required), it does not arm the clock, and — under a strict line of authority — a defective NOR does not automatically re-validate when the ship later becomes ready. Unless the CP has a saving clause, a fresh NOR may be needed. Time lost in the meantime becomes detention, argued on damages, not the tidy demurrage rate.
Statement of Facts (SOF)
The SOF is the chronological, timestamped record of the port call — the primary evidence for every laytime calculation and every demurrage claim. Produced by the port agent, it is signed by the master and usually a terminal/shipper representative.
A usable SOF records, with date and clock time:
- Arrival at the pilot station / anchorage / berth
- NOR tendered (and accepted)
- Commencement and completion of loading / discharging
- Every stoppage and its cause (rain, breakdown, shifting, awaiting cargo, awaiting documents, strike)
- Shifting between berths, surveys, draft checks
- Completion and unmooring
The SOF is the battleground. Ambiguous or unsigned stoppage entries are where demurrage claims are won and lost. A stoppage logged simply as "rain stopped work 1420–1655" is worth arguing over; the same stoppage logged as "rain — charterer's cargo not tendered" points liability in a very different direction.
How laytime is counted — the clause glossary
This is the reference the rest of the internet makes you hunt for. The charter party's counting clause decides which time counts. The common terms:
Which days count
| Abbreviation | Meaning | Effect on the clock |
|---|---|---|
| Running days / calendar days | Consecutive days, no exclusions | Everything counts — weekends, holidays, weather. |
| SHEX | Sundays & Holidays EXcepted | Sundays and holidays do not count. |
| SHINC | Sundays & Holidays INCluded | They do count. |
| FHEX | Fridays & Holidays Excepted | Muslim-calendar equivalent (Friday as the rest day). |
| SATSHEX / SSHEX | Saturdays, Sundays & Holidays Excepted | Weekend fully excluded. |
| EIU | Even If Used | Excepted periods stay excepted even if work is done in them. |
| UU | Unless Used | Excepted periods count if work is actually done (then only the time used, or the full period, per wording). |
Which conditions count
| Abbreviation | Meaning | Effect |
|---|---|---|
| WWD | Weather Working Day | A day on which weather permits work; time when weather stops (or would have stopped) work does not count. |
| WWDSHEX | Weather Working Days, Sundays & Holidays Excepted | The two rules combined — the most common dry-bulk basis. |
| Weather permitting | — | Time lost to weather is excluded even once counting has started. |
How the allowance is framed
| Term | Meaning |
|---|---|
| Reversible laytime | Load and discharge allowances are pooled; time saved at one end offsets time lost at the other. |
| Non-reversible | Each port stands alone; you can be on despatch loading and on demurrage discharging. |
| Averaging | Similar to reversible but the two calculations are netted at the end. |
| Laytime "as per CP" / fixed hours | A stated number of running hours (e.g. "72 hours WWDSHINC") rather than a rate. |
| Rate-based | Laytime = cargo quantity ÷ a daily rate (e.g. "10 000 mt per WWD of 24 consecutive hours"). |
Master these and you can read any charter party's counting regime. Get the abbreviation wrong and the whole calculation is wrong — this is the single most common source of demurrage error.
Worked example 1 — the clean case
Terms: 72 running hours SHINC. Demurrage €18 000/day. NOR tendered and accepted 10 Mar 0800; turn time 6 hours.
| Event | Date / time |
|---|---|
| NOR accepted | 10 Mar 08:00 |
| Laytime commences (after 6 h turn time) | 10 Mar 14:00 |
| Laytime allowed | 72 h → expires 13 Mar 14:00 |
| Discharge completed | 14 Mar 02:00 |
SHINC means weekends count, so the clock runs continuously. Laytime expired 13 Mar 14:00; completion 14 Mar 02:00 → 12 hours on demurrage.
Demurrage = 12/24 × €18 000 = €9 000
Clean, because nothing interrupted the clock.
Worked example 2 — weather and exceptions
Terms: 3 weather working days, Sundays & holidays excepted (WWDSHEX). Demurrage €18 000/day, despatch half. NOR accepted Fri 08:00; no turn time (laytime to commence on acceptance).
Allowed laytime = 3 WWD × 24 h = 72 h. Discharge finishes Tue 15:00. Count it day by day, applying the two rules separately — first the day-exception (is the day counted at all?), then the weather deduction (WWD):
| Day | Counts? | Weather | Laytime counted |
|---|---|---|---|
| Fri 08:00 → 24:00 | Yes (16 h available) | — | 16 h |
| Sat 00:00 → 24:00 | Yes (Sat not excepted here — only Sun & holidays) | −3 h rain (WWD) | 21 h |
| Sun | No — excepted (SHEX) | — | 0 h |
| Mon 00:00 → 24:00 | Yes | clear | 24 h |
| Tue 00:00 → 15:00 | Yes (15 h available) | clear | 15 h |
Running total: 16 + 21 + 0 + 24 + 15 = 76 h used against 72 h allowed → 4 h on demurrage.
Demurrage = 4/24 × €18 000 = €3 000
Had there been no Saturday rain, only 73 h would have been used → 1 h demurrage (€750). And under SHINC running days instead, Sunday's 24 h would have counted too — blowing laytime by Monday and running up far more demurrage. The lesson: the same physical port call yields wildly different money depending on whether the CP says SHEX vs SHINC and WWD vs running days. This is why an operator reprices a fixture the moment the counting clause changes — and why the calculator makes the clause an explicit input rather than a footnote.
Note on the weather deduction: we deducted the raw 3 clock-hours of rain for simplicity. Strictly, under the classic weather working day test (Reardon Smith Line v Ministry of Agriculture — "The Vorras"), you deduct the proportion of the working period the weather actually prevented work, not necessarily the exact stoppage clock-time.
Worked example 3 — reversible laytime
Reversible laytime pools the load and discharge allowances into one budget, so time saved at one end offsets time lost at the other. Terms: total laytime allowed 96 h reversible, demurrage €18 000/day, despatch half.
| Port | Laytime used |
|---|---|
| Load | 40 h |
| Discharge | 68 h |
| Total | 108 h |
Allowed (reversible) = 96 h
Used (both ports) = 108 h
On demurrage = 12 h → 12/24 × €18 000 = €9 000
Under non-reversible laytime the same facts settle differently: load would be despatch (48 h allowed − 40 h used = 8 h saved → 8/24 × €9 000 = €3 000 owed to charterer) while discharge would be demurrage (68 h used − 48 h allowed = 20 h → €15 000). Net €12 000 payable — versus €9 000 reversible. Same operations, a €3 000 swing purely from one word in the CP.
Demurrage in practice
"Once on demurrage, always on demurrage"
The defining rule. Once laytime is exhausted and the ship is on demurrage, the exceptions that paused the clock during laytime (weekends, weather) generally stop applying. Time then runs continuously until completion, unless the charter party contains an explicit clause that keeps a specific exception alive on demurrage (e.g. a "strikes exception to apply to demurrage" wording). Absent such a clause, weekend and weather stoppages during demurrage are the charterer's cost.
Demurrage is liquidated damages
The daily demurrage rate is agreed in advance as liquidated damages — the owner need not prove actual loss, and the charterer cannot argue the true loss was lower. It is pro-rated: half a day on demurrage is half the daily rate, calculated to the minute from the SOF.
Time bars kill good claims
Most modern charters impose a time bar on demurrage claims — commonly 90 days from completion of discharge — within which the owner must present the claim with all supporting documents (SOF, NOR, pumping logs, laytime calculation, notices). Miss the deadline, or omit a required document, and an otherwise valid claim is absolutely barred. Operationally this makes prompt, complete documentation more valuable than legal cleverness.
Despatch and detention
- Despatch rewards the charterer for finishing early. Two conventions: despatch on all time saved (all laytime saved) or on working time saved only (excepted periods don't count as saved). The rate is customarily half demurrage. Tankers usually have no despatch; dry bulk usually does.
- Detention is delay that falls outside the laytime/demurrage machinery — e.g. time lost after an invalid NOR, or delay caused by something the demurrage clause doesn't reach. It is damages at large: the owner must prove the loss, and there is no neat daily rate. Owners generally prefer to be on demurrage (certain, liquidated) than to argue detention (uncertain, proof-heavy).
Common disputes and traps
- Invalid NOR. Tendered before the ship was truly ready, or at the wrong place/time. Collapses the clock into detention. The single most common owner own-goal.
- Free pratique / customs. Whether pending pratique defeats readiness turns on the CP (see WIFPON/WICCON). Silent charters invite argument.
- Berth vs port charter. Decides whether time waiting at anchor for a berth counts. Misreading this misprices congestion risk entirely.
- Ambiguous SOF stoppages. "Rain stopped work" vs "awaiting charterer's cargo" allocate liability to opposite parties. Insist on cause, not just time.
- Shifting time. Time shifting between berths — does it count? Depends on the CP and whose account the shift is for.
- Exceptions on demurrage. Assuming weekends still pause the clock after laytime expires. They usually don't ("once on demurrage…").
- Reversible vs non-reversible. Netting load and discharge when the CP treats them separately (or vice versa).
- Time bar. A complete, correct claim filed on day 91 is worth nothing.
For developers and operators
The rynda demurrage tooling turns the SOF and the CP clauses into a defensible number.
- Laytime & demurrage calculator: enter the cargo, the laytime allowed (fixed hours or a rate), the counting clause (SHEX/SHINC/WWD…), the demurrage/despatch rates and the SOF events; it counts laytime, applies exceptions, and produces a laytime statement you can export to DOCX and attach to a claim. Scenarios are saved locally so you can compare "SHEX vs SHINC" or "6 h turn time vs none" side by side.
- Model the fixture before you fix it: because the counting clause is an explicit input, you can price the demurrage exposure of alternative wordings during negotiation, not after the dispute.
- Pair it with voyage economics: demurrage is one line in the voyage result; the voyage-economics calculator folds it into TCE alongside bunkers, port costs and the EU carbon layers.
- Call it as an API — or an LLM tool. The same engine is exposed as a public, no-auth endpoint:
POST /api/maritime-calc/tool/calculate_laytime_demurragetakes the fixture, the per-port SOF events and the CP rules (SHEX/SHINC, once-on-demurrage, despatch, time-bar) and returns allowed/used/balance hours, the demurrage or despatch due, the per-port breakdown and the time-bar deadline underresult:
curl -X POST https://rynda.io/api/maritime-calc/tool/calculate_laytime_demurrage \
-H 'Content-Type: application/json' \
-d @laytime.json
# → { "result": { … allowed/used/balance hours, demurrage or despatch due, time-bar … } }
Discover the input schema at GET /api/maritime-calc/tools, or import the OpenAPI spec at GET /api/maritime-calc/openapi into a ChatGPT custom GPT (Actions) or an MCP server.
FAQ and common confusions
Q: When exactly does laytime start?
A: After a valid NOR is tendered and any turn time / notice time in the CP has elapsed — not at the moment of arrival. If the CP says "laytime to commence 0800 next working day after NOR," an NOR at 1600 Friday may not start the clock until Monday.
Q: The ship was ready but had no berth — does waiting time count?
A: Under a port charter (often with WIBON), yes — congestion is the charterer's risk once the ship is an arrived ship and a valid NOR is tendered. Under a berth charter without such wording, generally no until the ship is in the berth.
Q: It rained for six hours after we were already on demurrage. Do we deduct it?
A: Usually no. "Once on demurrage, always on demurrage" — weather no longer pauses the clock unless the CP expressly keeps that exception alive on demurrage.
Q: What's the difference between demurrage and detention?
A: Demurrage is the agreed liquidated daily rate for staying beyond laytime — no proof of loss needed. Detention is delay outside the demurrage regime (e.g. after an invalid NOR) and must be proved as actual damages.
Q: How is despatch calculated?
A: Customarily half the demurrage rate, on time saved — either "all time saved" or "working time saved only," per the CP. Many tanker charters have no despatch at all.
Q: We have a rock-solid claim. Any deadline?
A: Almost certainly. Most charters bar demurrage claims not fully documented within a set window (commonly 90 days from completion of discharge). Present the SOF, NOR, laytime calc and supporting logs inside the window or the claim is barred.
Q: SHEX or SHINC — how much does it really matter?
A: Enormously. On a five-day port stay spanning a weekend, SHEX can exclude two full days of counting — often the difference between despatch and a five-figure demurrage bill.
Q: What is a Weather Working Day (WWD)?
A: A day on which weather permits cargo work. Time when weather stops work — or would have stopped it, had work been scheduled — does not count. It is judged against whether the specific cargo could be worked in that weather.
References
- Laytime Definitions for Charter Parties 2013 (BIMCO, CMI, FONASBA, INTERCARGO) — the standard vocabulary.
- Voylayrules 93 — an earlier standard set still referenced in some charters.
- Standard forms: GENCON (voyage), and commodity forms (e.g. grain, coal, ore CPs) with their own laytime clauses.
- Leading case law on arrived-ship and NOR validity (e.g. The Johanna Oldendorff, The Maratha Envoy line of authority) — consult a shipping lawyer for application.
- rynda laytime & demurrage calculator — reproduce and export any calculation here.
Document version
- 2026-07 — first public version. Vocabulary, method and worked examples for voyage-charter laytime and demurrage. The charter party wording always governs; this reference fills the gaps where it is silent.