Kayak Ferry Angle Calculator
Calculate the angle needed to paddle across a moving current without being swept downstream.
Enter current speed and paddle speed to get your ferry angle.
Reading a River Crossing
Pointing your kayak straight at the far bank and paddling hard does not work. The current will push you downstream the whole way. How much you get swept depends entirely on how your paddle speed compares to the current.
The Ferry Angle
To track straight across with zero downstream drift, you aim upstream by an angle called the ferry angle:
ferry angle = arcsin(current speed / paddle speed)
At 2 mph of current and 3 mph paddle speed: arcsin(2/3) = 41.8 degrees. You angle roughly 42 degrees upstream from the straight-across direction.
If the current exceeds your paddle speed, a zero-drift crossing is physically impossible. You will always be carried downstream regardless of boat angle.
Crossing Time
Once you have your ferry angle, your effective crossing speed perpendicular to the river is:
crossing speed = sqrt(paddle_speed squared minus current_speed squared)
Time to cross = river width / crossing speed
A 100-meter crossing at 2 mph current and 3 mph paddling: 100 / sqrt(9-4) = 44.7 seconds of active paddling.
Practical Notes
This assumes constant current across the full river width. Real rivers have faster flow in the center and slower near the banks. Many paddlers start with a larger angle and reduce it mid-crossing to compensate. Eddies at both banks change the entry and exit dynamics significantly. The calculation is most useful for planning; on the water you adjust continuously.