Current Deviation Calculator

This calculator is not designed to calculate the Course to Steer. It does demonstrate the deviations from the desired heading if currents are not compensated for. To calculate a course to steer: Go To: Course to Steer Calculator

The sailboat's speed as read on the GPS is a combination of both the current and boat power, as read on the boat's tachometer or knotmeter (the instrument on a sailboat which measures distance and is used to compute speed is called a "log" ) is reflective of the boat's power (it's speed in relationship to the water). This latter value is used in field #2 of the calculator.

The effects of current can be surprising. If a boat is traveling 6 knots in relationship to the water and is sailing against a 6 knot current, 45 degrees off the bow, the course deviation of the boat is 67.5 degrees. This is why it is usually best to sail with, rather than against, a strong current.

	*Current Deviation Calculator* 1. Enter the Speed in knots of the current: 2. Enter the speed in knots of the boat in relationship to the water as determined by the boat's knotmeter: 3: Enter the angle of the current to the boat's path (Bow being 0 degrees - Maximum Value is 90 deg):
	C : Is the angle of the Current to Boat's Bow sine C = c/a c = sine C * a cosine C = b/a b = cosine C * a d = power - b CD = arctangent ( c/d )

The values determined from this calculator should be used for educational purposes only. This calculator should not be used in determining the suitability of purchase, charter or passage on a boat. Instead the manufacturer should be contacted to obtain the boat's characteristics. The results of this calculator should not be relied upon for navigational purposes. US SAILING and its members assume no liability for the information presented on this website. The user is responsible to check the validity of all information.