What fuel reserve does MARPOL Annex VI require?

MARPOL Annex VI does not mandate a specific reserve quantity, but best-practice guidance from flag states and OCIMF recommends a minimum 48-hour steaming reserve on arrival at the next port. Many operators maintain 10–15% of voyage consumption as reserve. The IMO III Code (flag state instrument) may impose additional requirements for vessels on unmanned machinery spaces.

Why is a 48-hour fuel reserve recommended?

A 48-hour reserve is widely recognised as the minimum safety margin for commercial vessels. It covers weather delays, port congestion, engine efficiency drops, and deviation to an alternative port in an emergency. Many P&I clubs and charterers set this as a standing instruction in voyage orders.

How does weather routing affect fuel consumption?

Weather routing services (e.g., Applied Weather Technology, Bon Voyage System) can reduce fuel consumption 3–8% by avoiding heavy weather that increases resistance. ETA calculations should treat the fuel rate as a calm-water baseline and add a weather factor of 5–10% for exposed ocean passages, especially North Atlantic winter and Cape of Good Hope routes.

What is the typical reserve percentage of voyage fuel?

Industry practice is 10–15% of estimated voyage consumption as a reserve, but voyage orders and SMS procedures vary. Tankers under SIRE inspection are expected to hold at least 48 hours at sea speed. The calculated reserve in this calculator is a separate fixed buffer based on reserve hours — it is additional to the voyage fuel.

Passage time & ETA calculator

Enter distance, speed, and optional departure time to compute passage duration, ETA, and total fuel required — including a configurable bunker reserve. The industry minimum reserve is 48 hours steaming; many operators use 72 hours.

Distance (nm)

Great-circle or rhumb-line distance.

Speed (kn)

Average sea speed — add weather factor as needed.

Departure (local date & time)

Leave blank to skip ETA calculation.

Bunker reserve (hours)

Minimum 48 h recommended by P&I clubs.

Fuel consumption rate (MT/day)

Include HFO, MGO, or blended rate as appropriate.

Result

Passage time: 85h 43m
Voyage fuel: 107.1 MT
Reserve fuel: 90.0 MT
Total fuel required: 197.1 MT

Notes & caveats

· Passage time is computed as distance ÷ speed and does not account for current, current-set, manoeuvring time in port approaches, or pilot boarding delays.
· Fuel consumption is constant-rate; in practice consumption falls at lower speeds (approximately proportional to speed cubed). Recalculate if you slow-steam part of the voyage.
· ETA uses the browser's local time zone. Convert to UTC or port local time as required for notices of readiness and voyage reports.
· The total fuel figure does not include port consumption, aux boiler, or generator loads beyond the stated day rate. Add these separately.

Sources: MARPOL Annex VI; OCIMF Vessel Inspection Questionnaire; see also anchor scope calculator, ballast exchange calculator, notice of readiness.