A boat fuel cost calculator estimates how much fuel your boat will burn per hour and per trip based on engine horsepower, fuel type, and throttle setting. Whether you are planning a weekend fishing trip or budgeting for a full boating season, knowing your gallons per hour (GPH) helps you plan fuel stops, compare engine setups, and avoid running dry on the water.
Engine & Trip Details
Fuel Tank Range
| Throttle | GPH | Hours of Range | Cost to Fill |
|---|
Trip Planner (Distance & Speed)
Seasonal Cost Estimate
Cost Comparison
Your boat trip fuel cost compared to a day of other activities
How to Use the Boat Fuel Cost Calculator
Fuel is one of the largest ongoing expenses in recreational boating, yet most boat owners have only a rough idea of what each outing actually costs. This boat fuel cost calculator gives you a concrete estimate so you can budget for fuel stops, plan longer trips with confidence, and compare the running costs of different engine setups before you buy.
Step 1: Enter Your Engine Details
Start with your engine's rated horsepower. You will find this on the engine cowling for outboards, in the owner's manual, or on the manufacturer's specification sheet. If you have a multi-engine setup, select the number of engines. The calculator assumes all engines are the same horsepower, so for mixed setups use an average. Then choose gasoline or diesel. Gasoline marine engines burn approximately 0.10 gallons per hour per HP, while diesel engines burn about 0.055 GPH per HP at wide-open throttle.
Step 2: Set Your Throttle and Duration
Use the throttle slider or tap a preset to set your typical cruising speed. Most recreational boaters cruise at 60-70% throttle, which provides a good balance of speed and boat fuel consumption. Trolling for fish typically runs at about 25% throttle, while getting up on plane or running wide-open might hit 100%. Then enter how many hours you plan to be on the water with engines running. Sitting at anchor with the engine off does not count.
Step 3: Use the Trip Planner for Distance-Based Trips
If you know the distance in nautical miles but are not sure about trip duration, use the trip planner. Enter the distance and your estimated cruising speed in knots, and the tool auto-calculates hours and fills it in for you. This is especially useful for point-to-point coastal runs or crossing between islands.
Step 4: Review Your Results
After clicking Calculate, you will see gallons per hour (GPH), total gallons for the trip, total fuel cost, and cost per hour of operation. The fuel tank range table shows how many hours you can run at each throttle setting on a full tank, which is critical for safety planning. Always carry a reserve of at least 10-15% beyond your calculated fuel needs.
Seasonal Budgeting
The seasonal estimate section multiplies your per-trip fuel cost by the number of trips per month over your boating season. A typical season is six months, but this varies by region. This gives you a realistic annual fuel budget to compare against marina slip fees, insurance, and maintenance when calculating total cost of ownership.
Frequently Asked Questions
Is this boat fuel cost calculator really free?
Yes, completely free with no signup required. All calculations run locally in your browser using JavaScript. No data is sent to any server, and you can use it offline once the page loads.
Is my data safe when using this tool?
Absolutely. Everything is calculated in your browser. No engine specs, trip details, or fuel prices are stored or transmitted anywhere. Your privacy is fully protected.
How accurate is the GPH estimation formula?
The tool uses industry-standard rules of thumb: gasoline engines consume roughly HP x 0.1 GPH at wide-open throttle, and diesel engines roughly HP x 0.055 GPH. Real-world consumption varies by hull type, load, sea conditions, and engine age, but these formulas give a reliable planning estimate within 10-15%.
What throttle percentage should I use for cruising?
Most boaters cruise at 60-70% throttle, which balances speed and fuel efficiency. The tool includes presets: idle (10%), trolling (25%), cruising (65%), fast cruise (80%), and wide-open throttle (100%). Cruising at 65% is the most common setting for recreational boating.
How do I find my boat engine's horsepower?
Check the engine cowling or nameplate on outboard motors, your owner's manual, or the manufacturer's website. For inboard engines, the rated HP is usually listed on a plate on the engine block. You can also look up your engine model number online for exact specifications.
Does the calculator work for multi-engine boats?
Yes. Set the number of engines (1-4) and the calculator multiplies fuel consumption accordingly. Twin-engine setups are common on center consoles, while triple and quad engines are typical on larger offshore boats. Each engine is assumed to be the same horsepower.
How do I estimate fuel cost for a full boating season?
Use the seasonal estimate section at the bottom. Enter how many trips you take per month and the tool multiplies your per-trip cost over a typical 6-month boating season (April through September). This helps you budget annual fuel expenses alongside marina fees and maintenance.
What is the difference between gasoline and diesel fuel consumption?
Diesel engines are roughly 45% more fuel-efficient than gasoline engines of the same horsepower. The tool uses 0.055 GPH per HP for diesel versus 0.1 GPH per HP for gasoline. Diesel fuel typically costs more per gallon, but the lower consumption rate often makes diesel cheaper overall for high-horsepower boats.