Marine & Navigation

Under Keel Clearance Calculator

Assess UKC using depth, tide, squat, wave allowance, and safety margin.

Last validated: 2026-02-14

Under Keel Clearance Calculator computes UKC by combining charted depth, tide height, vessel draft, squat, wave allowance, and safety margin. It is useful for go/no-go checks in constrained channels and port approaches where depth margins are tight. The tool makes each allowance explicit, improving bridge-team discussion of risk tolerance. Use it for planning support and confirm with official depth, tide, and pilot guidance.

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Input Pattern

Enter values in the left panel, keep units explicit, run the calculation, then copy or share the result. Invalid fields are highlighted immediately.

UKC Inputs

Result

Available water: 7.200 m

Required depth: 5.300 m

Under keel clearance: 1.900 m

Transit status: Safe margin available

How to use this tool

Enter charted depth and expected tide height at transit time.
Add draft and dynamic allowances (squat, wave, safety margin).
Run the calculation and verify whether resulting UKC stays non-negative.

Worked Example

Auto-generated from the tool's current default or entered inputs.

Example Inputs

Charted depth m: 5.8
Tide height m: 1.4
Draft m: 4.2
Squat m: 0.4
Wave allowance m: 0.2
Safety margin m: 0.5
Available water m: 7.199999999999999
Required depth m: 5.300000000000001

Expected Outputs

Charted depth m: 5.8
Tide height m: 1.4
Draft m: 4.2
Squat m: 0.4

Interpretation

Charted depth m is 5.8. Use this as a decision input, not as a standalone conclusion.
Tide height m is 1.4. Use this as a decision input, not as a standalone conclusion.
Draft m is 4.2. Use this as a decision input, not as a standalone conclusion.
Cross-check the result against one alternate input set to validate sensitivity.

Scenario Compare (A vs B)

Use this to compare two input sets and quantify change in key outputs.

Scenario A

Charted depth m

Tide height m

Draft m

Squat m

Wave allowance m

Safety margin m

Available water m

Required depth m

Scenario B

Charted depth m

Tide height m

Draft m

Squat m

Wave allowance m

Safety margin m

Available water m

Required depth m

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Under Keel Clearance Calculator

Input Pattern

UKC Inputs

Result

How to use this tool

Worked Example

Example Inputs

Expected Outputs

Interpretation

Scenario Compare (A vs B)

Scenario A

Scenario B

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