Marine Fuel Consumption Calculator
Calculate fuel needed, trip time, cost, and range for your boat based on engine specs, speed, and distance.
About this calculator
This calculator estimates how much fuel a boat trip will burn, how long it will take, and what it will cost, from five inputs: cruising speed, fuel burn rate at that speed, one-way trip distance, the current price per gallon, and your boat's usable tank capacity. Trip time is simply distance divided by speed (hours = nautical miles / knots), and fuel needed is that trip time multiplied by the fuel burn rate you enter, so the burn-rate figure you supply -- ideally read from your own boat's performance at cruise, not a generic estimate -- drives the whole result. Fuel cost is fuel needed times fuel price, and a 10% reserve is added on top of the trip's ONE-WAY fuel needed to give a total recommended fuel figure -- that's a planning margin for the leg you entered, not a substitute for the standard "rule of thirds" (one third out, one third back, one third reserve) that real trip planning for a round trip should use.
Estimated range and fuel efficiency (nautical miles per gallon) both come from your entered tank capacity and burn rate rather than any trip-specific input: range is how far a full tank could carry the boat at the entered speed and burn rate, and efficiency is simply speed divided by burn rate. Fuel price does not affect fuel needed itself -- it only feeds fuel cost. Because the calculator has no information about sea state, wind, current, or hull condition, all figures are planning estimates, not guarantees -- always carry more fuel than the bare calculated minimum.
Inputs
Results
Fuel Needed
30 gal
≈ 6 buckets
How to Use This Calculator
- Enter your typical cruising speed in knots and your boat's usable tank capacity in gallons.
- Input the fuel burn rate in gallons per hour (GPH) at cruise — check your owner's manual.
- Enter the one-way trip distance in nautical miles and current marine fuel price per gallon.
- Review total fuel needed, trip time, and fuel cost for the one-way leg you entered.
- The 10% reserve adds a planning margin to the one-way figure only — for a round trip, double the fuel needed first and consider the boating rule of thirds.
How the result changes with Fuel Burn Rate
| Fuel Burn Rate | Fuel Needed |
|---|---|
| 6 | 15 gal |
| 9 | 22.5 gal |
| 18 | 45 gal |
| 30 | 75 gal |
What each input means
- Cruising Speed
- Average cruising speed in knots.
- Fuel Burn Rate
- Gallons per hour consumed at cruising speed.
- Trip Distance
- One-way trip distance in nautical miles.
- Fuel Price
- Current price per gallon of marine fuel.
- Tank Capacity
- Your boat's usable fuel tank capacity in gallons.
How this is calculated
Worked example, using the default values
- Identify Input Parameters5 parametersCruising Speed = 20, Fuel Burn Rate = 12, Trip Distance = 50, Fuel Price = 5.5, Tank Capacity = 60 = 5 input(s) provided
- Calculate Fuel NeededFuel Needed30 = 30
- Calculate Trip TimeTrip Time2.5 = 2.5
- Calculate Fuel CostFuel Cost165 = $165
Engine last updated . Checked against 1 independently-derived test — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Why doesn't fuel price change how much fuel the trip needs?
Fuel needed is calculated purely from trip distance, cruising speed, and the fuel burn rate you enter (gallons per hour at that speed) -- fuel price only multiplies the already-calculated fuel quantity to produce a dollar cost. Raising or lowering the price per gallon changes the trip's total cost but has zero effect on how many gallons the engine actually burns to cover the distance.
How is the estimated range different from the fuel needed for a specific trip?
Fuel needed answers "how much fuel does THIS trip burn," based on the distance you enter. Estimated range instead answers "how far could the boat go on a full tank," using the tank capacity you enter and the same burn rate -- so it reflects your actual boat rather than a generic guess, and should always be well above the fuel-needed figure for any trip the boat can realistically complete.
Does the 10% reserve fuel recommendation cover a round trip?
No -- the 10% reserve is added on top of the fuel needed for the ONE-WAY distance you entered, since that's what the Trip Distance field asks for. For an out-and-back voyage, double the fuel-needed figure before applying a reserve, and consider the boating "rule of thirds" (one third of your fuel out, one third back, one third held in reserve) rather than relying on a flat 10% margin for the return leg.
Does a faster cruising speed always mean better fuel efficiency in this calculator?
As this calculator computes it, yes -- efficiency (nautical miles per gallon) is cruising speed divided by fuel burn rate, so raising speed while holding the burn rate fixed raises the calculated efficiency. In real boating this trade-off is more complex because burn rate itself typically rises with speed, so use the burn rate you'd actually see at your intended cruising speed, not the value at a different speed.
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