Time-on-Time or Time-on-Distance? A Club Racer's Guide to PHRF Scoring

This is the argument that surfaces in every club bar at least once a season, usually somewhere between the second beer and the third. It is worth understanding properly, because it is one of the very few things about your racing that the race committee gets to choose, and because the choice is genuinely defensible in both directions.

Here is what each system actually does, where the arithmetic diverges, what the people who have studied it have found, and how to decide which one belongs in your sailing instructions.

Both systems start from the same number

The first thing to get straight is a distinction that most dock conversations skip: a handicap system and a scoring system are different things. As the PHRF of Lake Ontario paper puts it, a handicap system is the method that generates numbers representing a boat's speed potential. A scoring system is the mathematics used to correct a race with those numbers.

PHRF is a handicap system, and a performance-based one — it observes how boats actually go rather than predicting from measurement. It publishes one number per boat, in seconds per nautical mile. A rating of 180 means that for every rhumb-line mile of racecourse, that boat is credited 180 seconds against her finish time. Against a boat rated 174, the net advantage is six seconds per mile.

Time-on-Distance and Time-on-Time are two different scoring systems that consume that same published number. Neither one re-rates your boat. They just spend the number differently.

Time-on-Distance: subtract the allowance

The system almost every North American club grew up with. You take the course length in nautical miles, multiply by the boat's rating, and subtract:

corrected time = elapsed time − (PHRF × course distance)

Say you rate 72 and your rival rates 138, on a 6.0 nautical mile course. The difference is 66 seconds per mile, so over six miles you owe her 66 × 6 = 396 seconds, or 6:36. That number is knowable before the warning signal, it is written on the back of your hand, and it does not move for the rest of the evening. Whatever else you think of Time-on-Distance, that is a real virtue.

Time-on-Time: multiply by a factor

Time-on-Time throws the course length away entirely and multiplies elapsed time by a single per-boat number, the Time Correction Factor:

corrected time = elapsed time × TCF, where TCF = A / (B + PHRF)

The useful thing about that denominator, as John Collins explains in his primer for PHRF fleets, is that it isn't arbitrary. B + PHRF is the number of seconds the boat is assumed to take to sail one nautical mile in the expected conditions — divide it into 3600 and you get her assumed speed in knots. So the B constant is where "conditions" enter the arithmetic. The commonly used values:

• 480 — heavy air, or all off the wind
• 550 — average conditions
• 600 — light air, or all windward work

Collins is candid that "there are no hard and fast rules for selecting the B coefficient," and notes that the lower you set it, the more favourable the result is to the slower boats.

The A numerator is the part people agonise over unnecessarily. It exists only to make the TCF land near 1.000 for a mid-fleet boat so the corrected times look sensible. Collins is blunt: A has absolutely no effect on the corrected finish order. It changes the margins and nothing else. With a mid-fleet rating around 100 and average conditions, you get the formula most people have seen: TCF = 650 / (550 + PHRF).

If this sounds exotic, it shouldn't. It is what the rest of the offshore world already does. Under IRC, each boat carries a single Time Correction Coefficient — most cruiser-racers land between 0.900 and 1.100 — and her corrected time is simply elapsed time multiplied by her TCC. Same shape, different rating office.

The race where they agree exactly

Take two real-ish boats. Wind Chaser rates 72; Tidal Force rates 138. Under the Standard constants, their assumed paces are 622 and 688 seconds per mile — about 5.79 and 5.23 knots. Send them round a 6.0 nautical mile course on an evening that delivers precisely those speeds.

Both systems produce a perfect tie, and correctly so — these boats sailed identically well. The corrected times differ between the two columns, but that's cosmetic; only the order matters.

This is the single most useful fact in the whole debate, and it is easy to state: the two systems give the same answer when the race is sailed at the pace the ratings assume. The Southport Sailing Club analysis puts it formally — whenever your elapsed time equals your standard pace multiplied by the course distance, the time allowance is identical under both methods. Sail faster than your standard pace and Time-on-Time asks for less than Time-on-Distance would. Sail slower and it asks for more.

And the two evenings where they don't

Now run the same two boats round the same course on two different nights. On the first, the breeze never fills and everyone sails 30% slower than standard pace. On the second, it's a reaching blast and everyone goes 30% quicker. Crucially, in both cases both boats slow down or speed up by the same proportion — neither crew outsails the other.

That is the case for Time-on-Time in one table. The fixed allowance was correct for one particular race duration and quietly wrong for every other.

But be honest about what that demonstration assumes. It grants Time-on-Time its own premise: that when conditions change, boats slow down and speed up in proportion to each other. That premise is exactly what the other side disputes, and there is one situation where it plainly fails.

The case for Time-on-Distance

You know the number, and you can sail to it. Collins concedes this immediately: Time-on-Distance "is simple and you can tell exactly where you stand at any point in the race." Sailors do not experience a race as a spreadsheet. They experience it as a boat two hundred yards ahead that they either are or are not beating. A fixed allowance in seconds per mile gives you a target you can carry in your head from the first beat to the finish.

Writing for PHRF fleets in 1996, Russ Cardoza flagged this as the more important of the two objections. Sailors are used to thinking in distance, and under Time-on-Time "they lose their feel for the handicaps... they don't know how they're doing in the middle or at the finish of a race." Losing the plot mid-race is a genuine cost, not a rounding error.

The drifting match is a real problem. This is the strongest technical objection, and it deserves to be stated at full strength. When the wind dies and the fleet stops moving, the distance between boats stops changing — but the clock does not. Time-on-Time keeps handing the slower-rated boat more allowance for every minute that nobody is sailing anywhere. Cardoza's summary is that Time-on-Time "unfairly penalizes the fast boats if the wind dies during the race."

The Lake Ontario rejoinder is a practical one rather than a rebuttal: this "rarely results in significant errors since boats seldom completely stop during a race, and when they do, the race is frequently (and mercifully) abandoned due to time limitations." That is fair, but any race officer who has watched a fleet park in a dying sea breeze for forty minutes knows the failure mode is not hypothetical.

The ratings were built for it. PHRF numbers were defined for Time-on-Distance scoring, relative to a nominal zero-rated boat, and rating stations have spent decades tuning them under that assumption. Bolting a Time-on-Time formula onto numbers that were calibrated for a different arithmetic is a conversion, not a native fit — a point the Southport analysis develops at some length.

The case for Time-on-Time

The allowance should scale with the speed of the race. This is the whole argument, and the Lake Ontario paper makes it with a clean thought experiment. Two boats, one 10% slower, sailing a one-mile course. In a breeze they finish 80 seconds apart, so an 80 sec/mile difference in rating makes the race a dead tie under either system. Now sail the same course in half the wind. Time-on-Time still ties them. Time-on-Distance, with its fixed 80-second allowance, declares the faster boat the winner — even though "both boats were equally well sailed and should have tied."

Their conclusion is the point worth remembering: Time-on-Time "provides a first order correction for the speed of the race."

You stop having to measure the course accurately. This one is badly underrated. Time-on-Distance needs a course length, and the paper is unambiguous about what that costs: unless you have accurate electronic navigation gear or marks on known charted positions, there can be considerable error in estimating rhumb-line distance, and the handicap error is directly proportional to the error in the distance. Time-on-Time depends only on the accuracy of a clock, where "the error is negligible from a handicapping standpoint."

A related and very practical benefit: shortening course requires no extra thought. The same multiplier applies whatever length the race turns out to be. Under Time-on-Distance, every shortened course means recomputing a distance and re-issuing the allowances — usually in a hurry, usually on a wet clipboard.

It handles odd courses and wide fleets better. Cardoza's guidance is specific: Time-on-Time is fairer where rating differences within a class exceed about 20 seconds per mile, and where the course isn't a conventional beat-reach-run — an all-reaching sprint, say, or a light-air windward-leeward that takes forever. The Lake Ontario paper adds distance and port-to-port races, "where a balanced mix of upwind and offwind work cannot be guaranteed."

And the broader technical consensus leans this way. The Southport analysis notes that the velocity prediction programmes behind measurement handicaps support Time-on-Time as the better model of relative performance. It is what IRC does. It is what the rest of the offshore world does.

How much does this actually change?

Less than the intensity of the debate suggests — right up until it doesn't.

The Lake Ontario fleet, which has been scoring races both ways since the mid-1980s, reports that compared against the same results scored by Time-on-Distance, Time-on-Time has minimal effect on finishing places within division splits of 10 to 20 seconds per mile, and where a position does change, it is generally only one place. Cardoza agrees: there is effectively no difference for classes with small rating spreads sailing conventional beat-reach-run courses.

Collins describes the same pattern from the other end: Time-on-Time "will not turn a fleet upside down. It usually does not affect the top boats. It usually moves the boats in the middle around a little. If the handicap spread in a class is large, it will tend to tighten things up a bit."

So: if your Wednesday fleet is eight similar boats inside a 15 sec/mile band, this argument is close to academic and you should pick whichever your fleet finds easier to live with. If you are scoring one overall winner across a 26-footer and a 40-footer, the choice is doing real work and deserves real thought.

Choosing your constants matters more than you'd think

Here is the part that gets skipped. "Time-on-Time" is not one system — it is a family of them, and the B constant you pick moves the numbers considerably. Same two boats, same 66 sec/mile rating gap:

That is a 3:43 spread across the Time-on-Time options alone, on one race, from nothing but the choice of constant. And every one of those rows is somebody's published standard.

The Lake Ontario constants are the outlier, and they are contested. The Southport analysis is openly critical, calling the underlying 401.431 offset "unrealistically small (and peculiarly precise)" and noting it produces "wildly different results using time-on-distance versus time-on-time handicapping." The clubs on Lake St. Clair use a +557 sec/mile reconstruction instead. Neither side is being unreasonable; they are localising to genuinely different sailing areas with genuinely different average wind.

The practical rule that falls out of this: use the constants your rating authority publishes for your area, and don't invent your own. If your PHRF fleet issues a Time-on-Time multiplier on the certificate, that is the number to use. Choosing B by feel on the morning of the race is how a scoring system stops being a scoring system and starts being an opinion.

Getting your feel back on the water

If you do go to Time-on-Time, the "I can't tell how I'm doing" complaint has a fix, and Cardoza wrote the standard version of it in 1996. Stop thinking in seconds per mile and start thinking in seconds per ten minutes of racing:

seconds owed per 10 minutes = 600 × (rating difference) / (B + your rating)

For our two boats that is 600 × 66 / 622 = 63.7 seconds for every ten minutes you spend on the course. Round it to a minute. Round the mark forty minutes in and you need to be four minutes clear. Finish after an hour and a half and you need nine and a half. It is exactly as usable as a sec/mile number, and Cardoza's own observation is that the figure tends to come out close to the seconds-per-mile value you already had a feel for.

The Southport paper offers a neater variant for tracking several rivals at once. Every (B + your rating) seconds of your own elapsed time — 622 seconds, or about 10:22, for Wind Chaser — you must gain the raw rating difference on each competitor. So: every ten and a half minutes, take another 66 seconds out of Tidal Force. The interval depends only on your rating, so one number lets you track the whole fleet.

The third option: sail the handicap instead of scoring it

There is a way out of the whole argument, and it is the most spectator-friendly racing your club can run: spend the handicap on the start line rather than after the finish.

In a pursuit race, every boat is held back by her time allowance and released on her own gun, slowest first. The scratch boat leaves last and has to sail through the whole fleet. There are no corrected times, no TCF, no argument in the bar — the first boat across the finish line has won, and everybody watching can see it happen.

The trade is that you have committed to a distance-based allowance at the moment of the start, so a pursuit inherits Time-on-Distance's exposure to a race that runs long or short. What you buy with it is a finish that a ten-year-old on the clubhouse balcony can understand, which is worth rather more to a struggling weeknight series than theoretical precision is.

So which should you run?

A short decision guide, in the order the questions actually matter:

• Do you have a genuinely accurate course distance? If not, Time-on-Time, and the question is settled. A wrong distance corrupts every corrected time in proportion.
• Do you shorten course often? Weeknight series that shorten for fading breeze or fading daylight are a strong Time-on-Time case — nothing has to be recalculated.
• How wide is the class? Inside about 15 sec/mile, it barely matters; pick what your fleet already understands. Beyond about 20 sec/mile, Cardoza's guidance favours Time-on-Time.
• How conventional is the course? Windward-leewards in normal breeze suit either. All-reaching races, distance races and port-to-port races favour Time-on-Time.
• Does your venue die in the evening? A venue that reliably parks the fleet is the best remaining argument for Time-on-Distance, because that's the one place Time-on-Time's model genuinely breaks.
• Are you scoring an overall winner across the whole fleet? Then the choice is doing real work and should be made deliberately, published in advance, and left alone for the season.
• Do you want spectators to understand the finish? Run a pursuit.

The one genuinely bad answer is switching mid-series because of how last Wednesday came out.

Whichever you pick, write it down

This isn't optional, and it's the most common administrative failure in club racing. Under the Racing Rules of Sailing, rule A3 is what makes any of this binding: "when a handicap or rating system is used a boat's corrected time shall determine her finishing place."

Appendix J then tells you where to publish it. J1.1(4) requires the notice of race to state the classes racing, any handicap or rating system that will be used, and the classes it applies to. J1.3(5) covers the scoring system where it differs from Appendix A — and under J2.1(1), if that didn't make it into the notice of race, the sailing instructions must carry it.

In practice, one line does the job: "Boats will be scored using PHRF Time-on-Time, corrected time = elapsed time × 650 / (550 + PHRF)." Or the Time-on-Distance equivalent with the course distance stated. Two things to get right in that line: name the constants or the distance explicitly, and publish it before the first warning signal rather than after the first complaint.

One more worth knowing: rule A7 means exact ties on corrected time are a real possibility rather than a bug. Tied boats share the points for their place and the one below, divided equally.

Sources

1. John Collins, "Time on Time Scoring for PHRF" (PDF), August 2011 (the TCF = A/(B + PHRF) formula; what the denominator means; the 480/550/600 B factors; A has no effect on finish order; what to expect from a switch).
2. Russ Cardoza, "The Racer's Guide to Time on Time Scoring" (PDF), 29 July 1996 (the 20 sec/mile threshold; the loss-of-feel objection; the wind-dies objection; the seconds-per-ten-minutes conversion).
3. Steve Corona, "Time-on-Time Scoring: An alternative for PHRF" (PDF), PHRF of Lake Ontario (handicap system versus scoring system; the two-boat worked example in changing conditions; course-measurement error; shortened courses; the 10–20 sec/mile finding; the drifting-match caveat).
4. "Time-on-Distance versus Time-on-Time PHRF Handicapping on Lake St. Clair" (PDF), Southport Sailing Club (when the two systems give identical allowances; the VPP consensus; the tracking interval based on your own rating; the critique of the 401.431 offset and the +557 sec/mile reconstruction).
5. "What is IRC?", RORC Rating Office (single-number time-on-time rating; corrected time = elapsed time × TCC; typical TCC range).
6. The Racing Rules of Sailing 2025–2028, Appendix A (rule A3, corrected time determines finishing place; rule A7, ties on corrected time).
7. The Racing Rules of Sailing 2025–2028, Appendix J (J1.1(4), handicap or rating system in the notice of race; J1.3(5) and J2.1(1), the scoring system).
8. "Time On Time Scoring", PHRF New England (a regional fleet's published Time-on-Time guidance).