What VMG means
Velocity made good (VMG) is the part of your boat speed that brings you toward or away from the wind. A sailboat cannot sail straight into the wind, so it zigzags upwind. Sailing closer to the wind gives a better angle but less speed; bearing away gives more speed but a worse angle. VMG tells you which compromise gets you upwind faster.
The formulas
- VMG along the wind axis: boat speed × |cos(true wind angle)|
- VMC (velocity made good on course): boat speed × cos(angle between your heading and the bearing to the mark)
- Time to the mark: distance ÷ VMC
Example
At 6.5 knots and 45° from the true wind, you gain 4.6 knots straight upwind, 71% of boat speed. If pointing at 40° slows you to 5.8 knots, VMG drops to 4.44 knots, so footing at 45° is faster. With a mark 5 miles away and 30° off your heading, VMC is 5.63 knots and you would reach it in about 53 minutes if nothing changes.
Upwind and downwind
| True wind angle | Share of boat speed as VMG |
|---|---|
| 35° | 82% |
| 40° | 77% |
| 45° | 71% |
| 50° | 64% |
| 150° | 87% |
| 165° | 97% |
| 180° | 100% |
Downwind, sailing dead downwind gives the full speed as VMG, but most boats are slow there. Asymmetric spinnakers and fast boats gain a lot by gybing downwind at 135 to 150°, where they sail much faster.
Using VMG on the water
- Polar diagrams from the boat’s designer show target speeds and angles for each wind speed.
- Many instruments display VMG directly; steer to maximize it, not boat speed alone.
- In shifting winds, tack on headers and sail the lifted tack, which changes your effective angle.
VMC versus VMG
VMG compares progress against the wind direction. VMC compares progress toward a mark, which is what counts on a reaching leg or when the mark is not directly upwind. When the mark is dead upwind, VMC equals VMG.