Plan the whole trip
Boat fuel calculator
Estimate fuel from your own measured hourly burn. Enter engine time or total distance and speed, choose units, and add your own reserve. See the working, not just a number.
How to calculate boat fuel for a trip
Start with fuel use per hour measured on your own boat under comparable conditions. Include the full outing: the outward leg, return leg, and any other engine running. Do not infer a burn rate from horsepower alone. This tool never supplies engine performance figures.
Base fuel = hourly burn × engine hours. For distance mode, engine hours = total distance ÷ average speed over ground after converting both to compatible units. Added reserve = base fuel × reserve percentage ÷ 100. Total estimated fuel is base fuel plus that reserve.
Worked example: three engine hours
The illustrative inputs of 8 US gallons/hour and 3 hours produce 24 US gallons of base burn. A 50% addition is 12 gallons, giving 36 gallons in total. At ±20% burn, the same calculation gives a 28.8–43.2 gallon comparison band, including the same reserve percentage. This is arithmetic, not a recommended fuel load.
| Example input or result | Value |
|---|---|
| Whole-trip distance / speed alternative | 60 nautical miles / 20 knots = 3 hours |
| Base fuel | 8 × 3 = 24 US gallons |
| Added reserve | 24 × 0.50 = 12 US gallons |
| Total including reserve | 36 US gallons (about 136.27 liters) |
What does “reserve” mean here?
The BoatUS fuel-planning article describes a familiar thirds rule: a third outward, a third back, and a third held in reserve. If the full planned trip burns 24 gallons, retaining 12 gallons means starting with 36. Here reserve is an addition to expected trip burn; it is not a percentage of tank capacity. No percentage can account for every trip or condition.
Units and limits
The calculator uses US liquid gallons, never Imperial gallons. A US gallon is 3.785411784 liters, a nautical mile is 1,852 meters, and a statute mile is 1,609.344 meters. Knots mean nautical miles per hour. Conversions and calculations retain precision until display; numbers are rounded to two decimal places, with “less than 0.01” for small positive amounts.
Wind, current, load, hull condition, speed changes and detours can change consumption and time. The sensitivity band only explores the percentage you enter; it does not cover all uncertainty. It does not establish usable tank capacity, safe range, fuel availability, boat compatibility, navigation or weather suitability. Check your own vessel information and operating conditions.
Continue your launch plan
Find and compare Florida boat ramps, then use the editable boat launch checklist to organize preparation and retrieval.
Sources and method
- BoatUS: fuel planning and the thirds rule — planning context, not a burn-rate dataset.
- NIST: unit conversion factors — fuel, distance and speed conversions.
- NIST Handbook 133, Appendix E — exact customary unit definitions.
Method and sources checked October 19, 2026. Example figures are invented arithmetic inputs and are explicitly not vessel performance data.
Read alongside this tool
How to launch a boat · Boat fuel planning · Understanding ramp access