Fuel Per Navigation Leg Calculator
Calculate fuel required for each leg of a journey.
Plan fuel stops for sailing, boating, or long-distance driving routes.
Fuel Required
Fuel planning for a multi-leg journey requires calculating fuel burn per leg, then totalling across all legs — plus a safety reserve.
Core formula: Fuel per leg = burn rate × leg distance / speed
Or equivalently: Fuel per leg = burn rate × leg time
Where burn rate is in litres per hour (L/hr) or gallons per hour (GPH).
Safety reserves:
- IALA / RYA recommendation: Always carry 1/3 reserve beyond calculated fuel for motoring
- Offshore sailing: 20–25% reserve minimum
- General powerboating: 15–20% reserve
- Never plan to arrive with less than 10% fuel remaining
Fuel consumption examples:
Sailboat auxiliaries:
- 5 HP outboard (dinghy): 1–2 L/hr
- 15 HP inboard (daysailer): 2–3 L/hr
- 30 HP inboard (27-footer): 3–5 L/hr
- 75 HP inboard (40-footer): 8–12 L/hr
Powerboats:
- 90 HP outboard, 25 knots: 20–30 L/hr
- 200 HP sterndrive, 30 knots: 50–70 L/hr
Worked example: A 35 ft sailboat with a 30 HP engine burning 4 L/hr at 5 knots:
- Leg 1: 20 nm → 4 hours → 16 L
- Leg 2: 35 nm → 7 hours → 28 L
- Total: 44 L + 25% reserve = 55 L required