Tennis Rules and Scoring Explained: Games, Sets and Tiebreaks

The Rules of Tennis are published by the International Tennis Federation and run to a few dozen pages, of which club players need perhaps four. This section covers those four, and it exists because the questions that reach a coach most often are not about technique at all. They are about what the score is and whether a serve counts.

The scoring is genuinely strange, and inherited

15, 30, 40 came from real tennis, the older indoor game, when lawn tennis was codified in the 1870s. The clock-face explanation is the one usually given and may well be right, but it is not documented in the way a settled etymology would be. Anyone stating it as fact is overstating the record, which is worth knowing, because the same is true of "love" from l'œuf.

The two-point margin runs through everything

A game cannot be won from 40–40 by one point. A set cannot be won 6–5. A tiebreak cannot be won 7–6. The same principle repeats at every level of the scoring, and once seen it makes the whole structure predictable rather than arbitrary, including why set scores can only be 6–0 through 6–4, 7–5 or 7–6.

Serving is where most disputes happen

A fault costs one of two attempts; a let costs nothing and the serve is retaken. That distinction, plus what counts as a foot fault and what happens when the ball clips the net cord, accounts for most on-court disagreement in unofficiated play, which is nearly all tennis.

Approved alternatives, and why your league differs

No-advantage scoring, no-let, short sets and match tiebreaks are all permitted alternative procedures rather than different sports. Each competition publishes which it uses, and the entry conditions rather than general knowledge are what apply. A player arguing from the standard rules in a league that has adopted alternatives is arguing from the wrong document.

Where the rules and your league disagree

The published Rules of Tennis are narrower than most players assume, and a great deal of what gets argued about on court is a league or club convention rather than a rule. Whether a let is replayed on a first serve only, how many minutes of warm-up you get, whether coaching is permitted between sets, all of these vary by competition, and none of them is settled by knowing the rulebook.

The rulebook is also explicit that certain formats are approved alternatives rather than substitutions. Short sets, no-advantage scoring and match tie-breaks are all sanctioned, which means a league using them is not bending the rules, and it also means the format has to be agreed before the match rather than assumed from habit.

The practical position is that the rulebook settles what a fault is, what a let is and how the score works, and your competition's regulations settle everything about how the match is run. Disputes almost always turn out to be about the second, which is why quoting the first rarely ends them.

Line calls, and who decides

Almost all club and league tennis is played without officials, which means each player calls the lines on their own side and the ball is good unless they call it out. That default matters: a player who cannot clearly see the ball out has to play it, and "I think it was out" is not a call. The convention exists because the alternative, arguing from the far baseline about a mark thirty feet away, settles nothing.

A call also has to be immediate. A player who plays the ball, loses the point and then calls it out has forfeited the call, and the point stands. Where both players genuinely disagree and neither will concede, the accepted resolution is to replay the point rather than to split the difference on the score.

Doubles adds one wrinkle worth knowing: either partner may make the call, but if the two of them disagree with each other the ball is good. A team cannot resolve its own uncertainty in its own favour, which is a rule that comes up more often than most players expect.