Boat Fuel Consumption Calculator
Two Fuel Questions, One Piece of Math
"How much fuel will this trip take" and "how far can I go on what's in the tank" are really the same relationship viewed from opposite ends — both hinge on burn rate, speed, and time. This calculator handles both directions, so a passage can be checked against tank capacity before departure, or a tank's range can be estimated at a given cruising speed.
The Formulas
Time = Distance / Speed
Fuel Used = Time × Fuel Burn Rate
Range from Tank:
Endurance = Tank Capacity / Fuel Burn Rate
Range = Endurance × Speed
Worked Examples
| Mode | Inputs | Result |
|---|---|---|
| Fuel for a Trip | 150 nm at 10 knots, burning 6 gal/hr | 15.0 hr, 90.0 gal used |
| Range from Tank | 200 gal tank, burning 8 gal/hr, at 12 knots | 25.0 hr endurance, 300.0 nm range |
Where This Matters
- Pre-departure fuel checks — confirming the tank holds enough for a planned passage, plus a safety reserve, before leaving the dock.
- Speed-versus-range trade-offs — running the range calculation at a couple of different speeds shows how much throttling back extends how far the boat can go.
- Refueling stop planning — on a longer trip, comparing calculated range against leg distances identifies where a fuel stop is actually necessary.
Burn rate varies with engine load, sea state, and hull condition, so treat the result as a planning estimate and carry a fuel reserve beyond the calculated figure — conventional cruising practice is to plan around a "rule of thirds": a third of fuel out, a third back, a third in reserve.
How to Use This Calculator
- Choose the mode: Fuel for a Trip or Range from Tank.
- For Fuel for a Trip: enter Distance (nm), Speed (knots), and Fuel Burn Rate (gal/hr).
- For Range from Tank: enter Tank Capacity (gal), Fuel Burn Rate (gal/hr), and Speed (knots).
- Select Calculate to see fuel used, or endurance and range.
Related Calculations
Work out the distance for your route with the Marine Distance Calculator, or check hull speed limits with the Displacement Hull Speed Calculator.