Boat Fuel Consumption Calculator
At a 70% cruise, a gas engine burns about 1 gallon per hour for every 17 hp, so a 300 hp outboard uses about 17 gph. Diesel burns about a third less.
- Free, no signup
- Gas or diesel
- Statute or nautical units
- Range, reserve, and trip cost
Boat fuel consumption chart by horsepower
Gallons per hour for gas and diesel engines at a 70% cruise load and at wide open throttle, from the same formula the calculator uses. Use total horsepower: a pair of 150s is 300 hp.
| Total horsepower | Gas, 70% cruise | Gas, wide open | Diesel, 70% cruise | Diesel, wide open |
|---|---|---|---|---|
| 50 hp | 2.9 gph | 4.1 gph | 1.9 gph | 2.8 gph |
| 75 hp | 4.3 gph | 6.1 gph | 2.9 gph | 4.2 gph |
| 90 hp | 5.2 gph | 7.4 gph | 3.5 gph | 5.0 gph |
| 115 hp | 6.6 gph | 9.4 gph | 4.5 gph | 6.4 gph |
| 150 hp | 8.6 gph | 12.3 gph | 5.8 gph | 8.3 gph |
| 200 hp | 11.5 gph | 16.4 gph | 7.8 gph | 11.1 gph |
| 250 hp | 14.3 gph | 20.5 gph | 9.7 gph | 13.9 gph |
| 300 hp | 17.2 gph | 24.6 gph | 11.7 gph | 16.7 gph |
| 350 hp | 20.1 gph | 28.7 gph | 13.6 gph | 19.4 gph |
| 400 hp | 23.0 gph | 32.8 gph | 15.6 gph | 22.2 gph |
| 450 hp | 25.8 gph | 36.9 gph | 17.5 gph | 25.0 gph |
| 500 hp | 28.7 gph | 41.0 gph | 19.4 gph | 27.8 gph |
| 600 hp | 34.4 gph | 49.2 gph | 23.3 gph | 33.3 gph |
| 700 hp | 40.2 gph | 57.4 gph | 27.2 gph | 38.9 gph |
Assumptions: gasoline burns 0.50 lb per hp per hour and weighs 6.1 lb per gallon; diesel burns 0.40 lb per hp per hour and weighs 7.2 lb per gallon. Wide open means 100% load. The math is the same for outboards, sterndrives, and inboards. Hull, weight, prop, trim, and sea state all move real burn, so treat these as planning numbers.
How the boat fuel consumption calculator works
This free boat fuel consumption calculator estimates how much fuel your boat uses, how far you can run on a tank, and what a trip costs. If you have ever wondered how much fuel does a boat use, the answer comes down to engine horsepower, how hard you push the throttle, and whether you run gas or diesel. Enter your numbers above and the tool turns them into gallons per hour, miles per gallon, cruising range, and cost per mile.
How to use it
- Pick your boat type to load realistic values, or enter your own numbers and it switches to Custom.
- Set total horsepower, your typical cruise load percentage, and cruise speed.
- Add tank capacity and fuel price to get range and cost.
- Enter an optional trip distance to see trip time, fuel, and cost, and switch to nautical units if you think in knots and nautical miles.
Usable fuel holds back 10% of the tank. Tick the USCG 1/3 rule and it plans on a third out, a third back, and a third in reserve. When a trip needs more than your usable fuel, the calculator says so before you leave the dock.
Plan a specific trip
Want the distance, time, and fuel for a real passage? These route guides run the numbers for popular crossings and link back to this calculator with the trip pre-loaded.
Boat fuel consumption FAQ
How much fuel does a boat use per hour?
It depends on horsepower, throttle setting, and fuel type. A rough rule for gas engines is about 0.50 lb of fuel per horsepower per hour, and about 0.40 for diesel, at cruise. A 300 hp gas engine running at 70% load burns roughly 17 gallons per hour. Enter your own numbers above for an estimate tuned to your boat.
How does this boat fuel consumption calculator work?
It uses brake specific fuel consumption, the standard engineering measure of how much fuel an engine burns for the power it produces. Gallons per hour equals horsepower times load percentage times the fuel-burn rate, divided by fuel weight per gallon. From there it derives your miles per gallon, cruising range, and cost per mile.
What is a good fuel economy for a boat?
Most planing powerboats cruise somewhere between 1 and 3 miles per gallon. Heavy or fast boats can drop well below 1 mpg, while trawlers and displacement hulls running slow can do much better. Use the cruise-speed and load fields to find the sweet spot where your mpg is highest.
How do I figure out my cruising range?
Multiply your usable fuel by your miles per gallon. This calculator holds back a 10% reserve automatically, so the range it shows is what you can safely run before refueling. Enter your tank size to see the range estimate.
Does load and cruise speed really change fuel burn that much?
Yes. Pushing the throttle from a 65% cruise to wide-open throttle adds about 50 percent or more to gallons per hour, and the extra speed rarely makes up for it. Backing off a few hundred rpm is the single biggest lever on your fuel bill, which is why the calculator lets you test different load and speed settings.