How does tennis scoring work?

Tennis counts in three nested layers: points make games, games make sets, sets make the match.

Points within a game run 15, 30, 40, then game. Zero is called love. So a player leading 30–15 has won two points to one.

At 40–40 the score is deuce. From there a player must win two consecutive points. Winning one gives them advantage; winning the next takes the game. Losing it returns the score to deuce, and this can repeat indefinitely.

The server's score is always called first, which is why the same 30–15 is announced differently depending on who is serving.

Games within a set. The first player to six games wins the set, but must lead by two — so 6–4 wins, 6–5 does not. At 6–6 most sets are decided by a tie-break, played to seven points with a two-point margin, counted as ordinary numbers rather than 15/30/40.

Sets within a match. Most matches are best of three sets. Men's singles at the four Grand Slam tournaments is best of five.

As for why 15, 30, 40: the most widely repeated explanation is a medieval clock face, with points at the quarter hours and 45 shortened in speech to 40. The evidence is thin, and the origin is genuinely uncertain. Love for zero is often said to come from the French l'œuf, an egg for its shape, though that too is disputed.

Grand Slam final sets have used different tie-break rules over the years; since 2022 all four use a first-to-ten tie-break at 6–6.