About the Dead Reckoning Calculator
Estimated position after running a course and speed for a given time, with distance made good.
Also known as: dr position calculator, estimated position, navigation plot, course and distance.
How to use this calculator
- Enter speed, time run, course steered, current set (direction toward) and the other fields.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
position = course vector + current vector
Worked example
Using the values pre-filled in the calculator above:
- Speed = 6 knots
- Time run = 3 hours
- Course steered = 120 °
- Current set (direction toward) = 200 °
- Current drift = 1.2 knots
the calculator returns:
- Distance made good: 18.96 nm
- Course made good: 130.78 °
- Speed made good: 6.32 knots
- Distance through the water: 18 nm