What is the purpose of the 3 minute rule in navigation?

The 3-minute rule is a practical navigation tool used to determine how far a vessel will travel over a specific period of time, typically three minutes, based on its speed in knots. When a vessel is moving at a speed of 1 knot, it would cover approximately 100 yards in one minute, which means in three minutes, it would cover about 300 yards. Therefore, the 3-minute rule allows mariners to easily estimate the distance traveled in terms of yards when the speed is expressed in knots.

Understanding this calculation is essential for mariners to maintain situational awareness and navigate effectively, especially in confined waters or when approaching a waypoint. This rule simplifies the math and provides a quick reference for estimating distance during navigation, making it an invaluable tool for safe seamanship.