How do I calculate boat fuel consumption for a trip?

Divide trip distance by cruising speed to estimate running hours, then multiply hours by the total hourly fuel burn for all engines. Add a suitable reserve for conditions and safety planning.

What does GPH mean on a boat?

GPH means gallons per hour. It describes how much fuel an engine or group of engines consumes at a particular operating condition.

How much reserve fuel should a boat carry?

There is no single percentage suitable for every vessel or passage. The operator must account for applicable rules, weather, currents, sea state, alternate destinations, tank usability, and vessel-specific guidance.

Can horsepower estimate exact boat fuel burn?

No. A horsepower-based estimate is only a rough wide-open-throttle benchmark. Measured fuel flow or manufacturer performance data for the actual hull, engine, propeller, load, and RPM is more reliable.

Marine trip planner

Boat Fuel Consumption Calculator

Estimate hourly fuel burn, trip fuel, reserve, marina fuel cost, tank endurance, and cruising range using nautical or metric units.

Vessel and trip details

Trip distance

Distance unit

Cruising speed

Speed unit

Number of engines

Fuel-burn input

Burn rate per engine

Fuel volume unit

Additional trip reserve (%)

Tank capacity (US gal)

Fuel price per US gallon

Currency symbol

Trip fuel results

Fuel required with reserve—Expected burn plus selected reserve

Running time—

Total hourly burn—

Expected trip burn—

Reserve allowance—

Estimated fuel cost—

Cost per nautical mile—

Endurance with reserve held—

Range with reserve held—

Cross-unit fuel total—

Important planning note

This calculator is a budgeting and estimation aid, not a navigation, passage-planning, or safety system. Verify usable fuel onboard, required reserves, weather, sea state, currents, alternates, engine condition, and applicable regulations before departure.

How boat trip fuel is calculated

Boat fuel consumption is commonly tracked as gallons per hour or liters per hour at a known RPM and load. First calculate the expected running time, then multiply it by the combined burn rate of all engines.

Trip fuel = (distance ÷ speed) × burn per engine × engines

The calculator adds the selected percentage to expected burn for its “fuel with reserve” result. This is a simple additional reserve, not a claim that the percentage is appropriate for a particular voyage.

Range and tank reserve

Range uses tank capacity after holding back the selected percentage, then divides usable fuel by hourly burn and multiplies by cruising speed.

Range = tank × (1 − reserve %) ÷ hourly burn × speed

Published tank capacity may exceed safely usable capacity. Pickup location, trim, heel, contamination, and tank shape can leave fuel unavailable to the engine.

Example boat fuel calculation

A 60-nautical-mile trip at 18 knots takes approximately 3 hours 20 minutes. At 12.4 US gallons per hour, one engine is expected to burn about 41.33 gallons. Adding a 20% trip reserve gives 49.60 gallons. At $5.25 per gallon, the estimated fuel cost including that reserve is $260.40.

Frequently asked questions

Should I use GPH or MPG for a boat?

GPH is usually more useful because boat fuel burn changes sharply with RPM, hull resistance, load, wind, waves, and current. MPG or nautical miles per gallon can still help compare range at a known speed.

Where can I find my boat's fuel-burn rate?

Use a calibrated onboard fuel-flow instrument, measured fill-up records, or a manufacturer performance bulletin for the closest hull, engine, propeller, load, and RPM configuration.

How accurate is the horsepower estimate?

It is a rough wide-open-throttle benchmark based on generic fuel mass per horsepower-hour and fuel density. It cannot model hull efficiency, cruise RPM, propeller loading, engine technology, condition, or sea state.

Does the result account for wind and current?

No. Enter a conservative speed and measured burn that reflect the expected conditions, then evaluate additional contingencies separately.

Privacy and limitations

All calculations run locally in your browser. No route, vessel, cost, or fuel data is uploaded. Results are estimates and do not replace manufacturer documentation, onboard instruments, official requirements, or operator judgment.