Estimate fuel consumption from engine power, SFOC, and voyage profile. Supports single-leg and multi-leg voyages with speed–power scaling.
Enter your assumptions and voyage profile, then calculate.
| Leg | Distance (nm) | Speed (kn) | Time (h) | Propulsion Power* (kW) | Total Fuel (t) |
|---|
*Includes sea margin; auxiliary load is additional.
Preliminary operational estimate using constant SFOC and auxiliary demand. Verify against vessel-specific data; not a class-approved or contractual performance calculation.
Fuel consumption is one of the most important operational and economic parameters in marine transportation. Even relatively small changes in vessel speed, weather conditions, loading condition, or propulsion efficiency can significantly affect the total bunker consumption of a ship. For commercial operators, fuel usage directly influences voyage cost, emissions, charter performance, and operational profitability.
This marine fuel consumption calculator estimates ship fuel usage using engine power, voyage distance, vessel speed, specific fuel oil consumption (SFOC), auxiliary power demand, and sea margin assumptions. The calculator supports both simple single-leg voyages and more advanced multi-leg voyage calculations with speed–power scaling.
Results can be used for preliminary voyage planning, bunker estimation, fuel performance comparison, emissions analysis, and operational studies. The tool is suitable for displacement vessels including bulk carriers, tankers, container ships, offshore vessels, ferries, and general cargo ships.
Ship fuel consumption refers to the amount of fuel burned by a vessel’s propulsion and auxiliary systems during operation. In marine engineering, fuel consumption is commonly expressed in:
Fuel consumption depends on numerous operational and technical factors, including vessel displacement, hull resistance, engine efficiency, weather conditions, propeller efficiency, voyage speed, hull fouling, and auxiliary electrical demand.
In practice, fuel usage increases rapidly with speed. This is one of the most important concepts in marine operations and is the reason why slow steaming strategies became widespread across commercial shipping.
Ship resistance generally increases nonlinearly with speed. Because propulsion power is directly related to resistance, fuel consumption rises dramatically as vessel speed increases.
For many displacement ships, propulsion power approximately follows the classical propeller law:
P = Pref × (V / Vref)n
Where:
For conventional displacement vessels, the exponent is often close to 3. This means that a relatively small speed increase can produce a very large increase in required propulsion power and fuel consumption.
For example, increasing speed from 12 knots to 14 knots may increase daily fuel consumption far more than many operators initially expect. Because of this relationship, voyage optimization and economical speed analysis are major parts of modern marine operations.
The calculator uses standard marine engineering relationships based on energy consumption and engine fuel efficiency.
Total voyage time is estimated from distance and average vessel speed:
Time (h) = Distance (nm) ÷ Speed (kn)
Propulsion power is adjusted by the sea margin; auxiliary load is not:
PME, adjusted = PME × (1 + Sea Margin / 100)
Energy is calculated for each power source, then added for total energy:
Energy (kWh) = Power (kW) × Time (h)
Main engine and auxiliary fuel are calculated independently using their respective SFOC values:
FuelME (t) = PME, adjusted × Time × SFOCME ÷ 1,000,000
Fuelaux (t) = Paux × Time × SFOCaux ÷ 1,000,000
Fueltotal = FuelME + Fuelaux
Power is in kW, time in hours, and SFOC in g/kWh. Daily fuel consumption is total fuel divided by voyage days. Fuel per nautical mile is reported in kg/nm: total fuel in tonnes × 1,000 divided by total distance in nm. Multi-leg average speed is total distance divided by total voyage time.
Specific Fuel Oil Consumption (SFOC) represents the amount of fuel consumed by an engine to produce one kilowatt-hour of useful power. It is typically expressed in grams per kilowatt-hour (g/kWh).
Lower SFOC values indicate more efficient engines. Actual SFOC varies depending on engine type, engine load, tuning condition, fuel quality, ambient conditions, and maintenance condition.
Typical marine engine SFOC ranges include:
| Engine Type | Typical SFOC Range |
|---|---|
| Slow-Speed 2-Stroke Main Engine | 165–175 g/kWh |
| Medium-Speed 4-Stroke Engine | 180–205 g/kWh |
| Auxiliary Diesel Generator | 190–220 g/kWh |
Operators often use onboard performance reports and sea trial data to determine realistic SFOC values for operational calculations.
Sea margin is an additional power allowance applied to propulsion power calculations in order to account for real-world operating conditions. Ships rarely operate continuously in ideal calm-water environments.
Sea margin may account for:
Typical sea margins for commercial ships often range between 10% and 20%, depending on vessel type, service route, and operational philosophy.
In addition to propulsion power, ships consume fuel for auxiliary systems such as electrical generation, HVAC systems, pumps, cargo equipment, navigation systems, lighting, and accommodation services.
Passenger ships, offshore vessels, and reefer-heavy container ships may have particularly high auxiliary power demands. Including auxiliary load in fuel calculations produces more realistic operational estimates. This calculator applies a separate auxiliary SFOC, with no sea margin on auxiliary load. For electrical load, use SFOC per delivered electrical kWh, including generator losses. The default auxiliary SFOC is illustrative; replace it with applicable vessel data. Zero auxiliary load excludes auxiliary fuel.
The single-leg mode is suitable for straightforward voyage estimates where average speed and propulsion power remain relatively constant throughout the voyage.
The multi-leg mode allows each voyage segment to use different speeds and distances. SFOC, sea margin, auxiliary demand, and the reference speed–power relationship remain constant across all legs. This is particularly useful for:
Multi-leg calculations generally provide more realistic voyage fuel estimates compared to single-average-speed assumptions.
Real-world vessel fuel consumption may differ substantially from theoretical estimates. Actual operational performance depends on:
For commercial or compliance-related applications, calculations should always be verified using onboard measurements, noon reports, engine manufacturer data, and approved operational procedures. These preliminary estimates are not class-approved or contractual performance calculations.
Fuel consumption calculations are closely connected with propulsion, resistance, emissions, and voyage performance analysis. Related tools may include: