Time On Distance

  Corrected time is calculated as follows:

Corrected time = Elapsed time (ToD * Distance)

With Time-on-Distance (ToD) scoring, the coefficient of time allowance of one boat will not change with wind velocity, but will change with the length of the course. One boat will always give to another the same handicap in s/NM, and it is easy to calculate the difference in elapsed time between two boats needed to determine a winner in corrected time.

A special ToD coefficient calculated with an average crew weight of 170 kg is available for double handed racing as well as one calculated for non-spinnaker racing.


Where is it shown on the certificate?



Time on Distance scoring coefficients on simple scoring options on
ORC International and ORC Club certificates


How is it calculated?

  Coastal/Long Distance Time on Distance scoring coefficient also known as OSN (Offshore Single Number) is calculated as a weighted average of the predicted boat speeds in following conditions:


  8 kn 12 kn 16 kn  

The resulting time allowances at wind of 8 knots will be accounted with 25 %, the one at 12 knots with 50% and that at 16 knots with 25%.

The above scheme takes into account more windward/leeward directions in light winds, which is gradually reduced to have more reaching as the wind increases.

Beat VMG   40 % 30 % 20 %  
60   5 % 15 % 20 %  
90   5 % 10 % 15 %  
120   5 % 15 % 20 %  
150   5 % 15 % 15 %  
Run VMG   40 % 15 % 10 %  

Double handed coefficient is calculated with crew weight of 170 kg, while non-spinnaker rating is calculated for boat's performance without spinnaker. Double handed and Non-spinnaker ratings are given for both OSN and GPH calculations.

  Windward/Leeward Time on Distance scoring coefficient is calculated as the average of windward/leeward course (50 - 50 %) time allowances in three conditions multiplied by their respective weights:
       - 25 % of Windward/Leeward at 8 knots
       - 40 % of Windward/Leeward at 12 knots
       - 35 % of Windward/Leeward at 16 knots

A custom-made ToD coefficient may be calculated using a different wind distribution matrix based on wind historical data or weather forecast for a particular race. Course model to be used shall be specified in the Notice of Race and Sailing Instructions.


Handicap calculator

    Boat A     Boat B
ToD Coefficient     s/NM

ToD Coefficient

Length of Course     NM      
Elapsed Time    







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