Fuel Consumption At Sea Calculator

Work out fuel consumption at sea instantly with clear inputs, formula shown and shareable results.

About Fuel Consumption At Sea Calculator

Ship fuel consumption follows an approximately cubic law with speed, because resistance rises with the square of speed and power is resistance times speed. Dropping from 14 to 12 knots cuts daily burn by roughly 37%, which is the arithmetic behind slow steaming.

Formula

Cubic fuel law

burn = reference burn x (actual speed / reference speed)^3

Worked example

With the default values below, Fuel Consumption At Sea Calculator returns Daily consumption at actual speed of 17.63. Change any input above and every figure here is recalculated in your browser.

Inputs used

Reference daily consumption: 28 t/day
Reference speed: 14 kt
Actual speed: 12 kt
Voyage duration: 9 days

Results

Daily consumption at actual speed: 17.63 t/day
Fuel for the voyage: 158.69 t
Saving versus reference speed: 93.31 t
Consumption per nautical mile: 0.0612 t/nm

Step by step

1Values used
2Cubic fuel law
3Daily consumption at actual speed= 17.63 t/day
4Fuel for the voyage= 158.69 t
5Saving versus reference speed= 93.31 t
6Consumption per nautical mile= 0.0612 t/nm

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Marine results are planning estimates only. Verify against the vessel's approved stability booklet, loading manual, class society rules and applicable maritime regulations before loading or sailing.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Marine results are planning estimates only. Verify against the vessel's approved stability booklet, loading manual, class society rules and applicable maritime regulations before loading or sailing.

Frequently Asked Questions

Is the cubic law exact?

It is a good approximation in the displacement regime. Near hull speed or in heavy weather the exponent rises above three.

Does slow steaming always save money?

Fuel falls sharply but the voyage takes longer, adding charter hire, crew and cargo financing cost, so there is an economic optimum speed.