Eighty units aboard
With five unusable and a twenty-percent reserve, 60 units remain for planning before applying burn uncertainty.
Boat Cruising Range & Endurance Calculator
Created by: Emma Collins
Last updated:
Calculate arithmetic and planning endurance, cruising range, return radius, reserve fuel, and burn-rate sensitivity from measured vessel data.
Boat Cruising Range & Endurance Calculator
BoatingCompare absolute arithmetic endurance with a reserve- and uncertainty-adjusted planning range.
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What is a Boat Cruising Range & Endurance Calculator?
This calculator estimates endurance and nautical range from entered tank capacities, fuel aboard, unusable fuel, reserve policy, measured burn, speed, and uncertainty.
Planning range removes explicit reserve and increases measured burn. Absolute arithmetic range is also shown so the effect of the margins is visible, not because the fuel should be exhausted.
Actual range can be much lower and tank arrangement may prevent all fuel from reaching the engine.
How the Boat Cruising Range & Endurance Calculator Works
Tank capacities are totalled and current fuel is checked against that total. Unusable fuel is removed first.
Reserve is calculated as a percentage of physically usable fuel. Remaining planning fuel is divided by uncertainty-adjusted burn.
Endurance multiplied by speed produces range; half the planning range is displayed as a simplified return radius.
Formulas and assumptions
Planning fuel = current − unusable − reserve
Planning endurance = planning fuel ÷ [burn × (1 + uncertainty)]
Planning range = endurance × speed
Example Calculations
Out-and-back reference
A 100-nautical-mile planning range displays a 50-nautical-mile return radius, but opposing current or weather can make the two halves unequal.
Common Applications
- Fuel-stop planning
- Comparing reserve policies
- Range sensitivity
- Multiple-tank arithmetic
Fuel-Planning Tips
Match speed and burn from the same test condition.
Model head-current and rough-water cases separately.
Never plan to the arithmetic limit.
Frequently Asked Questions
Where should the burn-rate input come from?
Use repeatable measurements from the actual vessel or documented manufacturer data for the relevant engine, RPM, load, and conditions. Tank gauges and one short outing can be misleading. Keep the source, units, sea state, load, trim, fouling, and test method with the value.
What reserve percentage should I use?
The calculator deliberately does not prescribe one universal reserve. The skipper must choose a policy appropriate to vessel documentation, route, weather, current, traffic, fuel availability, transfer arrangements, local requirements, and safe alternatives.
Is calculated range or fuel use guaranteed?
No. Wind, waves, current, loading, fouling, trim, manoeuvring, idling, fuel quality, transfer problems, leaks, generator use, and mechanical condition can materially change consumption and usable fuel.
What is return radius?
It is half the calculated planning range, a simplified out-and-back arithmetic reference. It assumes the same speed and burn in both directions and ignores current, wind, detours, waiting, and a destination fuel source.
Why show absolute and planning range?
Absolute range uses physically usable fuel and entered measured burn with no reserve or uncertainty. Planning range removes the entered reserve and increases burn by the entered uncertainty. Neither is a safe operating limit.
How are multiple tanks handled?
Entered tank capacities are totalled, but the model does not simulate valves, transfer rates, cross-feed, list, trim, unusable fuel by tank, or whether all fuel can reach the engine.
Sources and References
- Royal Yachting Association. Passage Planning, accessed July 16, 2026; https://www.rya.org.uk/water-safety/passage-planning-and-navigation/passage-planning/.
- U.S. Coast Guard Auxiliary. Fueling and recreational boating safety resources, accessed July 16, 2026; https://wow.uscgaux.info/content.php?unit=B-DEPT.
- National Weather Service. Safe Boating and marine forecast resources, accessed July 16, 2026; https://www.weather.gov/safety/safeboating-marine.
- Mercury Marine. Propeller slip explanation and theoretical-speed convention, accessed July 16, 2026; https://www.mercurymarine.com/us/en/lifestyle/dockline/how-to-calculate-propeller-slip.
- Unit conversions and arithmetic assumptions are documented in each calculator method.
Planning limitation
Range is not guaranteed and return radius is not a safe boundary. Verify actual fuel, tank/transfer operation, forecasts, route, alternatives, and vessel documentation.