Slow Steaming Calculator
Quantify the trade-off between fuel savings and extra transit days when reducing speed below design. Uses the cubic law: halving speed roughly cuts consumption by a factor of eight.
Fill in the speed and route figures to see the slow-steaming trade-off.
How slow steaming savings are calculated
Fuel consumption at sea follows the cubic law: consumption scales with the cube of speed relative to the design speed. Slow steaming exploits this relationship to reduce bunker costs significantly, at the cost of longer transit times:
- Actual consumption per day = design consumption x (actual speed / design speed) ^ 3
- Transit days (design) = distance (nm) / (design speed (kn) x 24)
- Transit days (actual) = distance (nm) / (actual speed (kn) x 24)
- Fuel used (design) = design consumption x design transit days
- Fuel used (actual) = actual consumption per day x actual transit days
- Net fuel saving (USD) = (fuel used design - fuel used actual) x bunker price (USD/MT)
- Extra transit days = actual transit days - design transit days
A positive net fuel saving means slow steaming reduces costs. A negative figure means the chosen speed is above design, burning more fuel than the baseline. The extra transit days represent the time cost: factor in hire rate or cargo delay penalties before deciding whether the saving is worthwhile.
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Results are indicative only and do not constitute financial, chartering or legal advice. Verify against your charter party terms and current market data.