Fuel consumption calculator
Calculate total fuel for a passage from your engine's consumption rate, speed and distance.
Related tools
Worked example
A 60 nm coastal passage in a 30 ft yacht motoring at 6 knots, burning 3.5 L/hr:
- Journey time: 60 nm ÷ 6 kn = 10 hours
- Total fuel: 3.5 L/hr × 10 hr = 35 litres
- In UK gallons: 35 ÷ 4.546 = 7.7 UK gallons
- Fuel weight: 35 × 0.845 = 29.6 kg
- With 25% reserve: carry at least 44 litres
Try 3.5 L/hr, 6 kn, 60 nm above to verify.
Finding your consumption rate
Your engine manual gives consumption at various RPM. For passage planning, use the rate at your normal cruising RPM (typically 70–80% of maximum).
Always carry a reserve of at least 20–30% beyond your calculated requirement.
Frequently asked questions
How do I estimate fuel for a passage?
Multiply your engine's consumption rate (litres per hour) by your estimated journey time (distance ÷ speed). Then add a minimum 25% reserve for variable conditions, unexpected diversions and headwinds. Never plan to arrive with an empty tank.
What is a typical fuel burn for a 30 ft diesel cruiser?
A typical 20–35 hp diesel auxiliary in a 30 ft yacht burns 2–4 litres per hour at cruising RPM. Larger motor sailors with 40–60 hp engines typically burn 4–7 L/hr. Check your engine manual or measure over a known distance at sea.
Does sea state affect fuel consumption?
Yes, significantly. Motoring into a Force 4 head sea can double your fuel burn versus calm water. Allow a generous reserve when the forecast shows any wind-against-tide or swell. A 30% reserve becomes a 50% reserve in rough conditions.
Fuel weight reference
Diesel weighs approximately 0.845 kg/litre; petrol approximately 0.745 kg/litre. A full 100-litre diesel tank adds 84.5 kg to your boat — worth considering for trim and waterline.
Fuel weight matters
Diesel weighs approximately 0.845 kg/L. A 200L tank full of diesel adds about 169 kg.
Diesel: ~0.845 kg/L | Petrol: ~0.745 kg/L | Water: 1.0 kg/L