Marine Speed Made Good Calculator
Project your horizontal speed vector onto your chosen target direction using the relative angle.
A QUICK WALKTHROUGH
How to use this tool
- Enter your nonnegative horizontal speed and its unit.
- Enter the angle between that velocity vector and your target direction, then calculate.
- Calculate, then copy the report or download TXT.
Calculation
Signed projection = horizontal speed × cos(angle × π ÷ 180). An angle of 0° preserves speed, ±90° gives zero, and ±180° reverses the sign.
What the result covers
This is a plane projection of the velocity vector you supply. Positive means along the target direction; negative means against it. Currents, wind, changing headings and a safe route are not modelled. It does not provide navigation or safe-passage advice. When the target direction is the direction from which the true wind comes, this projection is wind VMG. Speed and angles must share the same reference frame. A projection toward an arbitrary waypoint is not automatically wind VMG.
Local processing
Inputs remain in your browser. Copy and TXT download contain your inputs, results, formula and scope note.
GOOD TO KNOW
Common questions
Can the result be negative?
Yes. A vector pointing more than 90° away from the target has a negative component along that direction.
Which speed should I enter?
Supply the speed vector you intend to project and match its reference frame to the target direction. The tool does not infer speed through water, speed over ground or environmental corrections. When the target direction is the direction from which the true wind comes, this projection is wind VMG. Speed and angles must share the same reference frame. A projection toward an arbitrary waypoint is not automatically wind VMG.