Compute Displacement/Length (D/L), Comfort Ratio, and Capsize Screening Formula (CSF) from displacement, LWL, LOA, and beam. Brief band labels only — not performance predictions.
Enter displacement (lb), waterline length lwl (ft), length overall loa (ft), and beam (ft).
Compute Displacement/Length (D/L), Comfort Ratio, and Capsize Screening Formula (CSF) from displacement, LWL, LOA, and beam.
Classic cruising ratios using saltwater density 64 lb/cu ft for CSF. Bands are rough labels only — not “guru” suitability claims for any ocean or crew.
D/L = (disp_lb ÷ 2240) ÷ (0.01 × LWL)³
Comfort = disp ÷ (0.65 × (0.7×LWL + 0.3×LOA) × beam1.333)
CSF = beam ÷ (disp ÷ 64)1/3
Use half-load or published displacement consistently.
Start with the calculator’s default entries: Displacement (lb) = 12000; Waterline length LWL (ft) = 28; Length overall LOA (ft) = 32; Beam (ft) = 10.5.
With those entries the calculator returns:
D/L 244
Comfort 27.5 · CSF 1.83 · moderate D/L band · CSF under 2 (more conservative label)
D/L = (12000/2240) ÷ (0.01×28)³ = 244.0 (moderate D/L band)
L = 0.7×28 + 0.3×32 = 29.20 ft
Comfort = 12000 ÷ (0.65×29.20×10.51.333) = 27.52
CSF = 10.5 ÷ (12000/64)1/3 = 1.835 (CSF under 2 (more conservative label))
Formula used: D/L = (disp_lb ÷ 2240) ÷ (0.01 × LWL)³ Comfort = disp ÷ (0.65 × (0.7×LWL + 0.3×LOA) × beam 1.333 ) CSF = beam ÷ (disp ÷ 64) 1/3
One input at a time. Raise Displacement (lb) from 12000 to 18000 and leave everything else alone. The result becomes:
D/L 366
Comfort 41.3 · CSF 1.60 · heavier D/L band · CSF under 2 (more conservative label)
D/L = (18000/2240) ÷ (0.01×28)³ = 366.1 (heavier D/L band)
Comfort = 18000 ÷ (0.65×29.20×10.51.333) = 41.28
CSF = 10.5 ÷ (18000/64)1/3 = 1.603 (CSF under 2 (more conservative label))
This sail design ratios page models the arithmetic shown in the formula box only.
D/L: under ~200 light; ~200–300 moderate; over ~300 heavy. Comfort: higher often read as more motion-friendly for size. CSF: under ~2 often labeled more conservative vs beamy; over ~2 more tender/beam-driven — rough labels only.
CSF here uses 64 lb/cu ft (salt). Freshwater density differs; do not mix units casually.
No — it is a screening number from older design literature, not a certification or voyage clearance.