Free Tool
UKC & Squat Calculator
Under-keel clearance = charted depth + tide − draft − squat − margin. Squat estimated by the Barrass formula.
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- Barrass squat Cb·V²/100
0.512 m - Depth + tide − draft − squat − margin
2.188 m
UKC = charted depth + height of tide − draft − squat − sea margin. Squat via the Barrass rule (Cb·V²/100, doubled for confined channels). Masters apply their own margins and tidal windows — indicative planning check, not a go/no-go for any transit.
Method
Barrass squat + master's margin.
Squat estimate
Cb·V²/100 metres in open water — doubled for confined channels, per the widely-used Barrass rule.
10% guideline
UKC below ~10% of draft is flagged marginal — many ports and masters use similar internal minima.
Planning check
Real transits use official depths, tidal windows and company policy — this screens, it doesn't clear.
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Draft feeds the cargo side too.
Check intake and deadweight before fixing the cargo.