Marine Fuel Consumption, Range & Trip Cost Calculator
Calculate safe cruising range, endurance and passage fuel cost with a proper reserve held back.
Last reviewed by the myCalculator Editorial Team
Input Parameters
A rough guide for petrol outboards is 0.4 L/hr per horsepower at cruise.
The one-third rule keeps a third of the tank for weather, tide and diversion.
Calculation Results
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Formula & How Marine Fuel Consumption, Range & Trip Cost Calculator Works
Marine fuel planning differs from road travel because there is no refuelling on the way and conditions change the burn rate significantly. Range is calculated from usable fuel after holding back a reserve, not tank capacity. The traditional one-third rule allocates a third of the tank out, a third back and a third in reserve — headwind, chop, a fouled hull or an extra passenger can all push consumption well above the flat-water figure. Worked example: with a 300 L tank and a 25% reserve you have 225 L usable. At 35 L/hr and 22 knots that is 225 ÷ 35 = 6.4 hours, or about 141 nautical miles of range. A 60 nautical mile passage takes 60 ÷ 22 = 2.7 hours and burns about 95 L, which at $2.15 per litre costs about $205. Sea state, loading and head winds raise the burn, so keep your reserve and carry more fuel for offshore trips.
- Enter Fuel Tank Capacity (L) (L): Input your target parameter value.
- Enter Fuel Burn at Cruise (L/hr) (L/hr): Input your target parameter value.
- Enter Cruising Speed (knots) (kts): Input your target parameter value.
- Enter Fuel Reserve (%) (%): Input your target parameter value.
- Enter Fuel Price ($/L) ($/L): Input your target parameter value.
- Enter Planned Passage Distance (NM) (NM): Input your target parameter value.
- Apply Formula: Calculate using
Range = (Usable Fuel / Burn Rate) × Speed | Fuel per NM = Burn Rate / Speed. - Review Results: View exact computed answers, metrics, and worked mathematical proofs.
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Frequently Asked Questions (FAQs)
How much fuel reserve should a boat carry?
The one-third rule is the accepted standard: a third out, a third back, a third in reserve. For coastal passages with no alternative fuel stop, many skippers hold a larger margin.
How do I estimate fuel burn without a flow meter?
A common approximation for petrol outboards is 0.4 L/hr per horsepower at cruise, and about 0.2 L/hr per horsepower for diesel. Verify it against tank readings over a known distance.
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Calculations and mathematical logic on this page are grounded in published statutory rules, regulatory standards, and official government data published by the following bodies:
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