Boat Fuel Consumption Calculator

Enter the specific fuel consumption, horsepower, and fuel-specific weight into the calculator to estimate the boat’s fuel consumption (typically expressed as gallons per hour at full power).

Boat Fuel Consumption Calculator

By Engine HP

Trip Planner

Estimates fuel burn from your engine’s horsepower and type.

Horsepower

Engine Type

Throttle Setting

Boat Fuel Consumption Formula

The following formula is used to estimate a boat engine’s fuel consumption.

FC = (SFC * HP) / FSW

Where FC is the fuel consumption at max throttle (gallons per hour, gal/hr)
SFC is the specific fuel consumption (typically in lb/(hp·hr))
- Gasoline (typical) ≈ 0.50 lb/(hp·hr)
- Diesel (typical) ≈ 0.38 lb/(hp·hr)
HP is the engine horsepower
FSW is the fuel specific weight (lb/gal)
- Gasoline ≈ 6.1 lb/gal
- Diesel ≈ 7.1 lb/gal

To calculate boat fuel consumption, multiply the specific fuel consumption (SFC/BSFC) by the engine horsepower to get fuel mass per hour, then divide by the fuel specific weight to convert to gallons per hour.

What is a boat fuel consumption?

A boat fuel consumption is a rate at which the engine on a boat consumes fuel, typically measured in gallons per hour.

The fuel consumption depends on the horsepower of the engine, throttle level, and type of fuel used.

How to calculate boat fuel consumption?

Example Problem:

The following example outlines how to calculate the fuel consumed by a boat engine.

First, determine the horsepower of the engine. In this example, the boat has one engine with a horsepower of 400 HP.

Next, determine the specific fuel consumption and fuel-specific weight of the fuel. In this example, the fuel is gasoline, so these values are 0.50 lb/(hp·hr) and 6.1 lb/gal respectively.

Finally, calculate the fuel consumption at max throttle using the formula above:

FC = (SFC * HP) / FSW

FC = (.50 * 400) / 6.1

FC = 32.787 gallons per hour

As a rough estimate, if fuel burn scales approximately with engine power, then at about half power you can divide the full-power fuel burn by 2 (actual results vary with engine efficiency and prop/hull load).

32.787 / 2 = 16.393 gallons per hour

Follow-Up Calculations

If your boat burns 6 gallons per hour while cruising at 18 mph, that works out to about 3 mpg — and at $4.50 per gallon, every mile costs roughly $1.50. You can use how far each dollar takes you to compare a slow, efficient cruise against a faster setting that gets you there sooner but uses more fuel.

A 24-gallon fuel tank adds about 149 pounds when full, so a day on the water that burns 12 gallons removes roughly 74 pounds from the boat as the trip goes on. Checking what your fuel tank weighs is useful for trim, payload, and planing performance, especially on smaller boats where weight changes are easy to feel.

If your engine burns 10 gallons per hour at cruise and makes about 150 horsepower, that comes out to roughly 0.41 lb of fuel per hp-hour, which is a practical way to judge whether the setup is efficient. The same idea applies when you compare fuel burn to output, helping you tell the difference between a healthy cruising load and an engine that is running less efficiently than it should.