Ship Fuel Consumption

This relation says that a ship’s required fuel rate grows very rapidly as speed increases: if speed doubles, the fuel burn rises by a factor of 8. The cubic dependence is an engineering approximation that comes from the fact that water resistance increases strongly with speed, and the engine must supply more power to overcome that drag. The constant c captures the hull shape, propeller efficiency, loading, and sea conditions, so different ships can have very different fuel use at the same speed.

Use this for quick estimates of how changing cruising speed affects fuel consumption on the same vessel in similar conditions. It is especially useful in voyage planning, cost trade-offs, and comparing fuel savings from small speed reductions.

• Using speed squared instead of speed cubed
• Forgetting that c depends on the specific ship and conditions
• Comparing fuel rates at different loads or sea states without adjusting the constant