What is VMG in sailing? Velocity Made Good explained

Put two identical dinghies on the same upwind leg. One reads 5.4 knots on the GPS, the other 5.0. Ask a group of club sailors which boat reaches the windward mark first and most will pick the faster one. Often they are wrong. The 5.4-knot boat may be sailing a lower, freer angle and covering more water to climb the same distance upwind. The 5.0-knot boat, pointing a little higher, can be making better progress toward the mark even though its speedo shows less. The number that settles the argument is VMG, velocity made good, and once you understand it, a lot of upwind and downwind sailing starts to make sense in a way that raw boat speed never explains.

Speed Is Not Progress

The core problem of sailing to windward is that you cannot point the boat where you want to go. The mark sits upwind, your boat sails at best somewhere around 40 to 50 degrees away from the wind on either tack, and so every meter of progress toward the mark is bought with extra meters sailed through the water. Boat speed tells you how fast you move along your heading. It says nothing about how much of that motion is actually taking you where you need to go.

Coaches sometimes draw ladder rungs on a whiteboard: imaginary lines across the course, perpendicular to the wind. Every boat on the same rung is equally far upwind, regardless of where it sits left or right on the course. Upwind racing is a climb up those rungs, and VMG is simply your climbing rate. A boat can be fast along the water and slow up the ladder. Another can be slower through the water and still climb past you. When sailors say a boat is "sailing high and slow" or "low and fast", they are describing two different bids for the same prize, and VMG is the judge.

What VMG Actually Is

VMG is the component of your boat speed that points directly upwind (or directly downwind, on a run). Take your speed vector, project it onto the wind axis, and the length of that projection is your VMG. If you prefer the formula, it is short:

VMG = boat speed × cos(angle to the wind axis)

Sail straight into the wind (impossible, but imagine it) and the angle is zero, cosine is 1, and VMG equals boat speed. Sail across the wind on a beam reach and the angle is 90 degrees, cosine is 0, and your VMG is zero: plenty of speed, no progress upwind at all. Everything interesting happens between those extremes.

A concrete case. You are beating at 45 degrees to the wind at 5.0 knots. The cosine of 45 degrees is about 0.71, so your VMG is 3.5 knots. You are climbing the ladder at 3.5 knots while moving through the water at 5.0. The missing 1.5 knots is the tax you pay for not being able to sail straight at the mark. All upwind technique, all rig tuning, all pointing-versus-footing debate is an attempt to reduce that tax.

The Pointing Versus Footing Trade-Off

Here is where VMG earns its keep. Point higher and the geometry improves: more of your speed counts. But sails generate less power at tighter angles, so the boat slows down. Bear away and the boat speeds up, but more of that speed is spent going sideways across the course. Both effects are working against each other all the time, and the best angle is wherever their product peaks.

Some plausible numbers for a hiking dinghy in a moderate breeze:

• Pinching at 40 degrees: 4.6 knots of boat speed, VMG 3.52 knots.
• The groove at 45 degrees: 5.0 knots of boat speed, VMG 3.54 knots.
• Footing at 50 degrees: 5.4 knots of boat speed, VMG 3.47 knots.
• Over-pinching at 30 degrees: 3.6 knots of boat speed, VMG 3.12 knots.

Two lessons hide in those numbers. First, the top of the curve is flat. Between 40 and 50 degrees the VMG varies by two percent, which is why good sailors describe the groove as wide in flat water and why small wobbles in steering are forgivable. Second, the curve is not symmetric. Ease too low and you lose gently. Squeeze too high and the boat stalls: at 30 degrees the same rig only drives the boat at 3.6 knots and your VMG collapses by more than ten percent. Pinching feels virtuous because the bow points at the mark, and it is usually the more expensive mistake.

Conditions move the optimum around. In chop you need power to punch through waves, so the best VMG angle moves lower and faster. In flat water and medium breeze you can afford to point. When a gust hits, the boat accelerates and the apparent wind shifts aft, letting you point higher for the same speed for a few seconds. None of this changes the principle. It only changes where the peak of the curve sits, which is why sailors talk about "shifting gears" rather than a single correct angle.

Polars: Your Boat's VMG Map

Plot your boat speed at every angle to the wind, for one wind strength, and you get a polar curve. It is the boat's fingerprint: close-hauled speeds on the upper part, reaching speeds bulging wide in the middle, running speeds at the bottom. Polars answer the VMG question graphically. Slide a horizontal line down from above until it just touches the curve, and the point where it touches is your best upwind VMG angle. Do the same from below for the downwind optimum.

Big boats get polars from the designer or a velocity prediction program. Dinghy sailors mostly do not, and published class polars describe a perfectly sailed boat in textbook conditions anyway. The more useful version is the polar you build from your own GPS tracks: hundreds of hours of your actual boat, your actual weight, your actual sails. That polar tells you not what the boat could do but what you currently do, and the difference between the two is your training plan. This is one of the reasons we built SailingMetrics to compute angles and speeds from plain phone or watch GPS tracks: you do not need a masthead wind sensor to start seeing your own curve emerge.

Downwind: Why the Longer Road Is Often Faster

Upwind VMG feels intuitive once explained, because everyone accepts that you cannot sail straight at the windward mark. Downwind is where VMG produces the advice that beginners find hardest to believe: do not sail straight at the leeward mark, even though you can.

On a dead run the sails work purely by drag and the apparent wind drops to true wind minus boat speed. Heat the angle up 30 or 40 degrees and the flow attaches, the apparent wind builds, and most boats gain far more speed than the extra distance costs. Say your boat runs square at 4.0 knots. Sailed 40 degrees off dead downwind it does 5.5 knots. The projection math gives 5.5 × cos(40°) = 4.2 knots of VMG, a five percent gain on the straight-line boat, and in most classes the real speed difference is larger than that. The faster the boat, the more extreme this gets: skiffs and foilers gybe through enormous angles and still demolish boats that point at the mark, because their speed gain at hot angles is not five percent but fifty.

Downwind VMG optimization is also more fragile than upwind. The run is where the fleet compresses, where pressure lanes matter enormously, and where sailing your theoretical best angle in dying breeze can park you while a competitor rolls over the top in a puff. Treat the polar optimum as the baseline you deviate from for tactical reasons, not a rule that overrides everything you can see on the water.

How Wind Strength Moves the Target

A single polar curve describes one wind strength, and the shape of the curve changes as the breeze builds, which means the best VMG angles move too. The pattern is consistent enough across boats to be worth memorizing.

In light air, sails need flow to generate any drive at all, and pinching kills that flow instantly. The optimum sits low and fast: wider angles upwind, and downwind angles so hot they feel absurd, sometimes 50 or 60 degrees off dead down in a drifter, because a boat that keeps moving builds its own apparent wind while a boat that runs square simply stops. Light-air races are lost by sailors steering the course they would sail in ten knots.

In medium breeze the boat reaches hull speed close-hauled with power to spare, and the spare power is best spent on height. This is where pointing wins, where the groove is widest, and where the numbers from the earlier sketch live.

In heavy air the calculation changes again, in different directions on the two legs. Upwind you are depowering anyway, so feathering slightly above the medium-air angle costs nothing and keeps the boat flat: the optimum creeps higher. Downwind, boats that plane or foil introduce a step into the curve. The moment a 49er or a foiling Moth gets onto its high-speed mode, its speed at a hot angle can double, and the polar grows a second bulge. The best VMG angle jumps from deep to hot almost discontinuously, which is why crews in these classes talk about downwind modes rather than angles, and why the answer to "should I soak low or heat it up?" can flip twice in one leg as the pressure comes and goes.

None of this needs to be memorized as a table. It falls out of one principle: the optimum angle is wherever extra speed stops paying for extra distance, and wind strength changes the price of both.

VMG Is Not VMC, and Wind Shifts Care About the Difference

A common confusion: VMG measures progress along the wind axis, not progress toward the mark. The related number, velocity made good on course (VMC), projects your speed onto the straight line between you and a chosen waypoint. On a perfectly square beat, where the mark sits dead upwind, maximizing VMG and getting to the mark fastest are the same project. The moment the wind shifts, they separate.

This matters practically. GPS chartplotters and watches often report VMC to a waypoint and label it VMG, and steering to maximize that number upwind will quietly encourage you to point at the mark, which is exactly the over-pinching mistake from the sketch above. The wind axis, not the mark, defines the geometry of a beat. Sail your best VMG angles on the lifted tack, take the shifts as they come, and the ladder rungs bring the mark to you. The only time to steer by VMC is when you can nearly fetch the mark and the question is whether to crack off and go straight. To build intuition for how much the shifts are worth, try the interactive wind-waves demo in our tools section: it shows how the same boat climbs the course faster or slower purely through timing its tacks against the oscillations.

The Instantaneous VMG Trap

Boats with instruments display live VMG, and the first thing every sailor does with it is chase it. Luff slightly and watch: VMG jumps, because the angle improved instantly while the boat keeps its old speed for a few seconds. The display rewards you. Then drag catches up, the speed bleeds away, the number sags below where it started, and the sailor bears away and gets the same false reward in reverse. Steering to live VMG produces a slow scallop that loses to a helm who just holds the groove. The physics guarantees it: boat speed responds to a heading change with a lag of several seconds to half a minute depending on the boat's weight, so the instantaneous number is always lying to you about the equilibrium.

Live VMG is still useful, but as a trim reference over stable stretches: hold your angle steady for thirty seconds, note the average, adjust one thing, compare. The honest version of the number is the average over a leg or over many tacks, which is exactly what post-session analysis is for. We have written a longer comparison of live metrics versus post-processing and where each one earns its place in training.

Measuring VMG Without a Full Instrument Package

To compute VMG you need two things: your velocity, which any GPS measures well, and the wind direction, which is the awkward part. Masthead wind gear is standard on yachts and rare on dinghies, and even good wind gear needs calibration to separate true from apparent wind. The practical alternative for most sailors is to work from the GPS track afterward.

A beat leaves an unmistakable signature in a track: two families of headings roughly 90 degrees apart, alternating at every tack. Split the difference and you have the wind direction to within a few degrees, with no hardware beyond the phone or watch that recorded the track. From there, every point of the track gets a VMG value, every leg gets an average, and tacks on port can be compared honestly against tacks on starboard. This is how SailingMetrics does it: upload a track, confirm or adjust the estimated wind direction, and the analysis reports VMG per leg, tack angles, and how much height each individual tack gained or lost. If you sail with a wind sensor or race with logged instruments, the imported wind data simply replaces the estimate.

A note on honesty in the numbers: GPS measures your motion over the ground, so current and tide are baked into every figure. On tidal water a leg's VMG mixes your sailing with the stream. For comparing two tacks sailed minutes apart in the same water this hardly matters. For comparing Tuesday against Saturday it can matter a lot, and it is worth remembering before drawing conclusions about your rig changes.

Putting VMG to Work

Knowing the theory changes little by itself. What changes boats is closing the loop between the number and a habit. Some ways to do that, roughly in order of effort:

• Learn your tacking angle. Your average angle between port and starboard headings on a beat is your tacking angle, and half of it is your angle to the wind. If you tack through 95 degrees and the local hotshots tack through 85, that difference compounds on every single beat. One number from one track, and you know where you stand. The tack itself is trainable too; we covered that in mastering the tack.
• Compare your tacks against each other. Average VMG on port versus starboard exposes asymmetries in technique, setup, or hiking that nobody notices while sailing. Differences of a few percent are common and correctable.
• Test settings back to back. Two rig setups, twenty minutes each on the same beat, compared by average VMG rather than felt speed. Feel lies; the projection does not.
• Train with a partner using speed tests. Line up two boats a few lengths apart, sail upwind for five minutes, compare VMG rather than distance ahead, since the boat that came out ahead on the water may simply have been on the favored side of a shift. Swap one variable and repeat. Putting both tracks on one map, cut into the same legs, is what course analysis is built for.
• Review the downwind legs, not just the beats. Most club sailors leave more VMG on the table downwind than upwind, because square running feels safe and nobody measures it. The track does not lie about how deep and how slow you sailed.

If you record your sailing anyway, the analysis side of this costs nothing extra. Upload the track, look at the VMG per leg, find the one number that is furthest from where it should be, and make that the focus of the next session. Repeat for a season and the compounding is remarkable.

Common Questions

What is a good VMG? There is no universal number, because VMG scales with boat speed and wind strength. A Laser beating in twelve knots might make 3.5 knots of VMG; a TP52 in the same breeze makes more than double that. The useful comparisons are relative ones: your VMG against your own past sessions in similar conditions, against your training partner on the same beat, or against the ratio benchmark of your class. As a rough sanity check, displacement dinghies typically make an upwind VMG of 60 to 75 percent of their close-hauled boat speed. If your ratio is well below that, the tacking angle is usually the first place to look.

Is higher VMG always better? Over a whole leg, yes, by definition: more VMG means reaching the next mark sooner. At any given moment, no. Sailing into a header to reach better pressure, ducking a starboard boat, or holding a lane off the start line all sacrifice VMG now for more of it later. The number is the measure of the outcome, not a steering instruction for every second of the race.

Why is my VMG sometimes negative? Because you were moving away from the wind axis reference, which happens legitimately at every mark rounding and pre-start, and also happens when the wind direction used in the calculation is wrong. A track analysis that shows negative VMG in the middle of an honest beat is nearly always using a stale wind direction, which is worth correcting before believing anything else in the report.

Do I need instruments to use any of this? No. Every number and every comparison in this article can be computed from a phone or GPS watch track after sailing, with the wind direction estimated from the tacking pattern. Instruments add live feedback and better wind data; they do not gatekeep the analysis.

The Short Version

Boat speed measures motion; VMG measures progress. Upwind and downwind, the fastest route is almost never the one that points closest to the mark, and the best angle is a trade between geometry and boat speed that shifts with wind and waves. The top of the VMG curve is forgivingly flat, but pinching past it is punished quickly. Downwind, sailing extra distance at hotter angles usually wins. Do not chase the live number; trust the averages. And you do not need instruments to start: a GPS track and an honest look at the angles will tell you more about your upwind sailing than any amount of dockside theory.