SEA CALCULATOR
UKC & squat
UKC worksheet: depth, tide, squat and company minimum margin.
Open water (default): squat ≈ K × Cb × V² / 100 with K = 1. Confined channel: K = max(1, 5.74 × S^0.76) from blockage S = (beam × draught) / (channel width × water depth). Highest speed for required UKC: V ≈ √(allowed squat ÷ (K × Cb / 100)). UKC-1 worked example below uses open water — leave confined unchecked.
SMS example only: some companies use about 10% of static draught — type your own minimum in metres below. That is separate from the CATZOC depth allowance (e.g. CATZOC B on this form adds 1.30 m uncertainty to the charted depth).
Depth of water = 15.0 + 1.6 = 16.60 m
Squat ≈ 0.650 m
Dynamic draught = 13.950 m
Gross UKC = 2.650 m
CATZOC allowance = 1.30 m
Net UKC (after CATZOC) = 1.350 m
Squat here uses the Barrass method, an empirical estimate. Use your ship's own squat data where you have it.
Estimate only, from a standard published method. Check against your ship's data, the official publications and your company procedures.