Marine & Navigation

CPA/TCPA Risk Calculator

Compute closest point of approach and time to CPA with risk banding.

Last validated: 2026-02-14

CPA/TCPA Risk Calculator estimates closest point of approach and time to CPA using relative motion vectors from ownship and target kinematics. It is useful for watchstanding triage of collision risk and prioritizing contacts that need early action. The tool also maps computed values to a simple risk band for quick operational interpretation. Use it as support data, not as a substitute for continuous lookout, radar/AIS cross-checking, and proper maneuvering practice.

Permalink

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.

CPA/TCPA Inputs

Result

CPA distance: 1.604 nm

TCPA: 24.24 min

Risk level: LOW

How to use this tool

Enter own course/speed and target bearing/range/course/speed.
Run computation to obtain CPA distance and TCPA minutes.
Use risk banding to prioritize contacts for closer monitoring and maneuver planning.

Worked Example

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

Example Inputs

Own course deg: 85.0
Own speed kn: 14.0
Target bearing deg: 40.0
Target range nm: 8.5
Target course deg: 190.0
Target speed kn: 12.0
Cpa nm: 1.6041023110923138
Risk level: low

Expected Outputs

Own course deg: 85
Own speed kn: 14
Target bearing deg: 40
Target range nm: 8.5

Interpretation

Own course deg is 85.0. Use this as a decision input, not as a standalone conclusion.
Own speed kn is 14.0. Use this as a decision input, not as a standalone conclusion.
Target bearing deg is 40.0. 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

Own course deg

Own speed kn

Target bearing deg

Target range nm

Target course deg

Target speed kn

Cpa nm

Risk level

Scenario B

Own course deg

Own speed kn

Target bearing deg

Target range nm

Target course deg

Target speed kn

Cpa nm

Risk level

Explore more versions

Tailored guides for specific audiences, regions, and scenarios.

core

Collision-avoidance systems

Promote AIS tools, radar integrations, and electronic navigation systems.

CPA/TCPA Risk Calculator

Input Pattern

CPA/TCPA Inputs

Result

How to use this tool

Worked Example

Example Inputs

Expected Outputs

Interpretation

Scenario Compare (A vs B)

Scenario A

Scenario B

Explore more versions

CPA/TCPA Risk Calculator

CPA/TCPA Risk Calculator for Germany

CPA/TCPA Risk Calculator for United Kingdom

CPA/TCPA Risk Calculator for United States

Collision-avoidance systems