Squat and under keel clearance calculator

At speed in shallow water the ship sinks and usually trims, so the clearance under the keel is smaller than at rest. Squat grows with the square of the speed: slowing down is the quickest way to win back clearance.

Result

Squat0.80 m

Dynamic draft13.30 m

Clearance under way1.70 m

Highest speed for the required clearance13.7 kn

Clearance is above the required value

How it is calculated

Barrass (2004): maximum squat ≈ Cb × V² ÷ 100 m in open water and Cb × V² ÷ 50 m in a confined channel, V in knots. It is an estimate: use the pilot's and port's figures and the company's UKC policy.

Reference only. The maker's manual and class rules take priority.

Reference table

kn \ Cb	0.60	0.70	0.80	0.85
4	0.10 / 0.19	0.11 / 0.22	0.13 / 0.26	0.14 / 0.27
6	0.22 / 0.43	0.25 / 0.50	0.29 / 0.58	0.31 / 0.61
8	0.38 / 0.77	0.45 / 0.90	0.51 / 1.02	0.54 / 1.09
10	0.60 / 1.20	0.70 / 1.40	0.80 / 1.60	0.85 / 1.70
12	0.86 / 1.73	1.01 / 2.02	1.15 / 2.30	1.22 / 2.45
14	1.18 / 2.35	1.37 / 2.74	1.57 / 3.14	1.67 / 3.33

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