Capsize Screening Formula Calculator
The Capsize Screening Formula (CSF) calculator evaluates a monohull sailboat's resistance to capsize in rough open waters. Developed by US Sailing following the tragic 1979 Fastnet Race, a rating under 2.0 is generally required for ocean racing and blue-water passages.
Understanding the Capsize Screening Formula
The Capsize Screening Formula (CSF) was created by the Cruising Club of America (CCA) and US Sailing in the aftermath of the 1979 Fastnet Race, where severe ocean weather caused multiple boats to capsize. It serves as a rapid preliminary screening tool to check a boat's vulnerability to capsizing in breaking waves.
How to Interpret Your Score
- Under 2.00 (Pass): The sailboat is considered sufficiently stable and adequately ballasted relative to its beam for offshore passages and ocean racing.
- 2.00 or Higher (Caution): The vessel is wider or lighter relative to its weight, making it more prone to capsizing when struck by large breaking waves. Recommended primarily for coastal or inland sailing.
The Formula Explained
The mathematical formula compares the boat's beam (width) to its volumetric displacement:
Note: Dividing displacement in pounds by 64 converts the weight to cubic feet of seawater. Because this formula is built around imperial units, metric inputs (meters/kg) are automatically converted to feet and pounds before calculating the final rating index.