Laytime and Demurrage Calculator: Days and USD

Formula, assumptions, and limits

Demurrage is the agreed daily sum the charterer pays when loading and discharging exceed the allowed laytime; despatch, where granted, is the (conventionally half-rate) sum the owner pays back for laytime saved. To calculate the settlement, net used against allowed on the basis the charter states:

t_allowed - laytime allowed, from the charter party: a fixed number of days and hours, or computed from cargo quantity and the CP rate (a 60,000 t cargo at 10,000 t per weather working day allows 6 days). t_used - laytime used, from the statement of facts after the charter’s counting rules are applied. r_dem / r_des - demurrage and despatch rates per day, from the recap.

Per-port laytime settles each port on its own equation, and despatch at one port coexists with demurrage at the other. Reversible laytime pools the allowances: one combined figure, one settlement, with saved time at the load port directly offsetting excess at discharge. The charterer normally holds the option, exercises it after the figures are known, and picks whichever basis settles cheaper; the calculator shows both so the comparison is explicit.

What the arithmetic does not do is build the used-time figure. Laytime counting is the contested ground of every demurrage claim: when notice of readiness could validly be tendered, when laytime commenced after it, whether the terms were weather working days, SHINC or SHEX, and which interruptions counted. Those determinations happen on the statement of facts against the charter’s words, and their output, a number of days and hours used, is this calculator’s input. Once on demurrage, the exceptions generally stop counting in the charterer’s favor, which is why a laytime statement distinguishes time before and after the allowance ran out.

How to use this calculator

1. Enter the allowed laytime at load and at discharge from the charter party.
2. Enter the used laytime at each port from the laytime statement.
3. Choose per-port or reversible, as the charter provides.
4. Enter the demurrage rate, and the despatch rate where the charter pays it.
5. Read the days and USD per port and for the voyage, on both bases where the option exists.

The counting terms behind the used figure

The same SOF produces different used figures under different terms, which is why the laytime statement quotes the charter’s exact words before it counts a single hour. The BIMCO Laytime Definitions 2013 standardize the weather and hatch terms when the charter adopts them; SHINC and SHEX are not 2013-defined terms, so modern forms define them in the clause itself, and older fixtures and bespoke riders depart freely. The departure governs.

Worked example

A 60,000 t coal cargo, 3 days allowed at load and 3 at discharge, demurrage USD 22,000 per day, despatch half demurrage. The statement of facts yields 4.2 days used at load and 2.5 at discharge. Per-port: load is 1.2 days on demurrage (USD 26,400), discharge saves 0.5 days for USD 5,500 despatch, netting USD 20,900 to the owner. Reversible: 6.7 days used against 6.0 pooled, 0.7 days on demurrage, USD 15,400. The charterer’s option is worth USD 5,500 on this voyage, which is exactly why the option exists and why owners price it. Rates are the fixture’s own; these figures are illustrative.

Common errors

1. Pricing part days as whole days. Demurrage accrues pro rata unless the charter says otherwise; 1.2 days at USD 22,000 is USD 26,400, not USD 44,000.
2. Applying despatch where none is agreed. Most tanker forms pay no despatch; assuming half-rate despatch on a Shellvoy fixture invents money.
3. Netting per-port figures when the charter is non-reversible. Saved discharge time cannot offset load-port demurrage unless reversibility was agreed; the bases are mutually exclusive alternatives.
4. Feeding SOF elapsed time in as laytime used. Elapsed time between arrival and completion includes periods that never counted; the input is the laytime statement’s net figure (the laytime-used builder assembles it from port events), not the calendar gap.
5. Confusing charter demurrage with container D&D. A box sitting past free time at a terminal accrues the carrier’s demurrage and detention tariff per container; that is a different charge under a different contract, and this page’s laytime arithmetic does not compute it.

About This Laytime and Demurrage Calculator

The laytime settlement is the voyage charter’s financial endgame: the clock the fixture wound at the negotiating table, read out against the statement of facts. This calculator is for owners, charterers, operators, and demurrage analysts who hold the allowed and used figures and need the settlement priced: per port, reversible, or both for the comparison the charterer’s option demands.

The arithmetic follows the standard forms: excess time at the demurrage rate, saved time at the despatch rate where granted, pro rata for part days, with the reversible basis pooling the allowances the way the BIMCO Laytime Definitions describe. The despatch-half-demurrage convention is the default the rate fields carry, and both fields take whatever the recap actually says.

The chart sets used against allowed at each port with the excess and the saving shaded, so the shape of the voyage’s clock is visible before the USD lands. The used-time figure itself comes from laytime counting against the charter’s terms, covered with worked counting rules in the laytime and demurrage articles; the claim this settlement becomes must then survive the charter’s time bar, and multi-port voyages pool across calls in the multi-port reversible calculator.

Further reading

• Laytime
• Demurrage
• Reversible laytime and despatch
• Demurrage time bar calculator
• Multi-port reversible calculator

Frequently asked questions

What is the difference between laytime, demurrage, and despatch?

Laytime is the time the charter party allows for loading and discharging. Demurrage is the agreed daily rate the charterer pays when cargo operations exceed the allowance. Despatch, where the charter grants it, is the (usually half-rate) amount the owner pays back for laytime saved. One clock, three outcomes.

How is demurrage calculated?

Demurrage equals the time used beyond the allowed laytime, multiplied by the charter-party demurrage rate, normally pro rata for part days. Used time comes from the statement of facts after applying the charter's counting rules: when laytime commenced after notice of readiness, and which periods (weekends, holidays, weather) counted.

What does reversible laytime mean?

Reversible laytime pools the load and discharge allowances into one figure at the charterer's option, so time saved at one port offsets time used at the other. Per-port (non-reversible) laytime settles each port separately, and saved time at one port cannot rescue an overrun at the other.

What does 'once on demurrage, always on demurrage' mean?

Once the allowed laytime is exhausted, the laytime exceptions (weekends, holidays, weather interruptions) generally stop protecting the charterer, and demurrage runs continuously unless the charter expressly interrupts it. The phrase is a working presumption of construction, not an absolute rule: clear words in the charter can provide otherwise.

Is this the same as container demurrage and detention?

No. Charter-party demurrage is liquidated damages under a voyage charter for exceeding laytime, settled between owner and charterer. Container demurrage and detention (D&D) is the carrier's per-container charge for boxes sitting past free time at a terminal or off it; that calculation runs on free days and per-day tariffs per box, not on this page's laytime arithmetic.

Is despatch always half the demurrage rate?

By convention, yes: 'despatch half demurrage' is the standard fixture term, but it is a term, not a law. Some charters pay no despatch at all (notably most tanker forms), and some agree other fractions; the recap governs.