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Fuel Range Calculator

Calculate boat fuel range from tank capacity, cruising speed, and consumption rate. Plan passages and refueling stops for powerboats and sailboats.

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Inputs that matter
Fuel Capacity, Fuel Consumption, Cruising Speed, Reserve Fuel
Output to expect
Fuel Range Calculator
  • Check the units and required inputs before comparing results.
  • Keep the assumptions with a copied result so you can reproduce the calculation later.
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Reference & details

How it works

Fuel Consumption Rate

Consumption in gallons or liters per hour at a given RPM and load. Manufacturer specs or measured burn at cruise throttle provide the base rate.

Burn rate (GPH) at cruise RPM from engine spec or flow meter

Range Calculation

Range equals usable fuel divided by consumption, multiplied by speed. Apply 20–33% reserve — never plan to empty the tank.

Range (nm) = (usable fuel / GPH) × speed (knots)

Speed-Fuel Tradeoff

Fuel consumption rises roughly with speed cubed on displacement hulls. Reducing speed 10% can reduce fuel burn 25–30% on many powerboats.

Fuel ∝ speed³ (displacement hull approximation)

Updated: July 2026

Example Scenarios

Cruise at 7 knots burning 3 GPH. Usable 80 gal (20% reserve): range = (80/3) × 7 ≈ 187 nm. Plan refuel stops every 150 nm for margin.

At 12 knots: 8 GPH, 60 gal usable → 90 nm range. At 9 knots: 4 GPH → 135 nm range. Slowing 25% nearly doubles range.

30 gal diesel, 1.2 GPH at 5.5 knots motoring: (24 gal usable / 1.2) × 5.5 = 110 nm engine range for calm-no-wind contingency.

Common Mistakes to Avoid

Planning range to empty tank

Fuel gauges are inaccurate, especially near empty. Plan arrival with 25–33% reserve minimum. Running out of fuel at sea is a leading cause of towing calls.

Using WOT fuel burn for cruise range

Wide-open throttle consumption is 2–3× cruise burn. Range calculations must use the RPM and throttle setting you actually cruise at.

FAQ

Minimum one-third tank for powerboats; never less than 20%. Passage planning should include reserve for weather delays, current against you, and engine inefficiency.

Run at cruise RPM for one hour and note fuel used from flow meter or tank gauge change. Repeat in loaded condition — consumption increases with weight and sea state.

Yes. Head seas and wind increase engine load at the same GPS speed. Add 15–30% consumption allowance for rough conditions on passage plans.

Displacement hulls push water aside — power needed scales with speed cubed. Planing hulls have a hump speed; just below planing is often worst efficiency.

Use nautical miles for marine navigation — GPS and charts are in nm. Convert statute mpg × 0.869 for nautical miles per gallon.

About Fuel Range Calculator

Fuel range planning prevents running dry on long passages. This calculator estimates nautical range from tank capacity, fuel burn rate at cruising RPM, and speed, with reserve allowance for safety.