Engine
Speed and consumption
What slowing down (or speeding up) does to fuel per day and per mile: the saving from slow steaming, or the cost of making up time.
3 for most ships (2.7–3.3)
Fill in the fields to see the result.
How it works
Near the design speed, the power a propeller needs grows with the cube of the speed, so fuel per day ∝ speed³ and fuel per mile ∝ speed². From 14 to 12 knots, the daily consumption falls by about 37% and the fuel for the same distance by about 26%, while the passage takes 17% longer.
The exponent is usually between 2.7 and 3.3 depending on the hull and draught; the default is 3. Weather, fouling and draught change the real figures, and running a main engine at very low load has its own limits: follow the maker's guidance.
For training and cross-checking. Not a substitute for approved navigation equipment, nautical publications and the ship’s own procedures. Calculations run in your browser and nothing you type is stored; a PDF you download is made on our server and not kept.
More tools
All tools- Port to port distances
- Compass error
- Great circle and rhumb line
- Speed, distance, time and ETA
- Current triangle
- Compass error by the sun
- Sunrise, sunset and twilight
- Dead reckoning position
- Distance off
- Sextant altitude and noon latitude
- Required speed for an ETA
- CPA and TCPA
- True wind
- Horizon and light range
- MLC hours of rest
- Ship’s clocks and time zones
- IMO and MMSI number check
- Dock water allowance and loading
- Height of tide
- Mean draught and trim
- GM from rolling period
- Squat and under-keel clearance
- Anchoring
- Search patterns (IAMSAR)
- Fuel consumption and endurance
- Propeller slip
- Indicated power
- Bunker quantity
- Fuel heating temperature
- Cylinder oil feed rate
- Electrical power
- Pay and contract dates
- Unit and position converter
- Signal flags and phonetic alphabet
- COLREGs lights and shapes
- Beaufort and sea state scales
- Marine VHF channels