How is laytime allowed calculated?

Laytime allowed is the cargo quantity divided by the agreed handling rate in tonnes per day, summed across loading and discharging ports. For example, 30,000 tonnes loaded at 10,000 t/day allows 3 days for loading, plus the discharge allowance.

What is the difference between demurrage and despatch?

If the ship is detained beyond the allowed laytime, the charterer pays demurrage at the agreed daily rate for the extra time. If cargo work finishes early, the owner often pays despatch for time saved, conventionally at half the demurrage rate.

Why is despatch usually half of demurrage?

Despatch at half demurrage (DHD) is a long-standing charter-party custom: the owner shares the benefit of fast cargo work but at a lower rate than the penalty for delay. The exact ratio is whatever the charter party specifies, so always check the clause.

What is the difference between lumpsum and per-tonne freight?

Lumpsum freight is a fixed sum for the whole voyage regardless of cargo loaded, shifting quantity risk to the charterer. Per-tonne freight multiplies an agreed rate by the cargo quantity actually carried, so freight rises and falls with the loaded tonnage.

Does this account for reversible laytime?

This tool totals load and discharge time together, which is equivalent to reversible laytime where time saved at one port offsets time lost at another. For non-reversible terms, calculate each port separately and do not net the surplus and deficit.

Charter Party Freight Calculator

Settling a voyage charter means agreeing two numbers: the freight earned for carrying the cargo, and the demurrage or despatch arising from how fast that cargo was loaded and discharged. This calculator does both from the charter-party terms.

How it works

Freight is either a fixed lumpsum or a rate times the cargo loaded. Laytime allowed is the cargo divided by the agreed handling rate; comparing it with time actually used gives demurrage or despatch:

freight        = lumpsum   OR   rate_per_tonne × cargo_tonnes
laytime_allowed = cargo / load_rate + cargo / discharge_rate   (days)
time_used       = load_time + discharge_time                   (days)
if time_used > allowed:  demurrage = (used − allowed) × demurrage_rate
if time_used < allowed:  despatch  = (allowed − used) × despatch_rate

Despatch is conventionally paid at half the demurrage rate (despatch half demurrage), but the charter party governs the exact figure.

Example and tips

For 30,000 tonnes at 25 per tonne, freight is 750,000. Loading at 10,000 t/day and discharging at 15,000 t/day allows 3 + 2 = 5 days of laytime. If the ship actually used 6 days, the charterer owes one day of demurrage; at a 20,000/day rate that is 20,000. Had cargo work finished in 4 days, the owner would pay one day of despatch at the half rate, 10,000. Make sure the handling rates and the demurrage rate come straight from the charter party, and confirm whether laytime is reversible before netting load and discharge time.