How fast you are closing in on your destination or next waypoint, the part of your speed that points at it.
VMC (velocity made on course) is the part of your speed that brings you directly toward a destination, usually the next waypoint. It's the same idea as VMG, but measured against the bearing to the mark instead of the wind direction.
Calculation
VMC = speed × cos(angle between your course and the bearing to the waypoint)
- Heading straight for the waypoint: VMC equals your speed.
- 30° off: about 87 % of your speed counts.
- 90° off: VMC is zero, so you're not getting any closer.
Chartplotters calculate VMC from SOG and COG, so the current is included.
VMC or VMG
When the destination lies straight upwind or downwind, VMC and VMG are the same. When it doesn't, they differ: VMG tells you how well you're beating against the wind, VMC how fast you're getting to where you actually want to go. On a passage, VMC is the number to watch; sailing a little lower and faster can bring a better VMC than steering straight for the mark.