How tennis scoring works

Call the score before the umpire. Know which point matters.

Key facts

1
A tennis game is four points with a two-point margin, so from deuce, 40-40, you need two points in a row to win it.
ITF Rules of Tennis
2
A set is six games with a two-game margin, and 6-6 goes to a tiebreak.
3
Matches are best of three almost everywhere and best of five in men's singles at the Grand Slams.
4
The earliest reference usually cited for the 15, 30, 40 scoring is quarante-cinq, forty-five, in a 1435 ballad by Charles d'Orléans. The origin itself is disputed.
Wikipedia, "Tennis scoring system"
5
The clock-face story for 15, 30, 40 is probably a myth, because minute hands appear to postdate the scoring.

Why it works

A game is four points with a two-point margin. At deuce you need two in a row: advantage, then game. Lose the second and it's deuce again. No-ad scoring replaces that loop with one deciding point. The same win-by-two rule repeats at every level: points into games, games into sets, sets into a match.

That structure is why some points matter more. The scoring is largely memoryless, so given each player's chance of winning a point on serve, you can compute the chance of winning the match from any score. A point's leverage is how far that chance swings on winning or losing it. A break point at 5-6 in a deciding set has enormous leverage. 40-0 at 3-0 has almost none.

The names are folklore. "Love" as l'oeuf, French for egg, is contested. "Deuce" likely comes from à deux, two to win. The 15, 30, 40 sequence has medieval French references, a clock-face story that fails on dates and a competing theory from jeu de paume.

The line to say on court
“Four points, win by two. Then again, and again, and again.”

Drill: Call it first

40 min · alone

Watch one set of any match with the score graphic covered. After every point, say the score aloud before the umpire or the caption does.
At deuce, say "advantage" or "deuce" for the next two points before they're shown.
Before each point, say "big" or "small" for how much you think it matters.

Number to beat20 points in a row with the score called correctly before the umpire

More drills like this: watch like an analyst

Faults and fixes

Thinking 40-40 is game point

From deuce you need two points in a row.

FixSay "deuce" and count to two.

Thinking first to four points wins

It only wins with a two-point margin.

FixWatch the gap, not the count.

Telling the "love" origin as fact

The origin is contested.

FixTell it as a story, not a fact.

Believing 40 is 45 shortened from a clock face

The clock story is shaky on the dates.

FixCall it disputed.

Questions players ask

What is deuce in tennis?

Deuce is 40-40. From deuce a player needs two points in a row: the first gives advantage, the second wins the game. Lose the point after advantage and it goes back to deuce.

Why is tennis scored 15, 30, 40?

Nobody knows for sure. The popular clock-face story probably doesn't fit the dates, because minute hands seem to have come later. There are medieval French references and a competing jeu de paume theory.

How many games are in a set of tennis?

A set is won by the first player to six games with a two-game margin. At 6-6 the set goes to a tiebreak.

Which points matter most in tennis?

Points near the end of a game where a break comes into view. At 30-40 the break point moves the match most, 30-30 next and the opening point least.

What this doesn't cover

Leverage depends on the assumed chance of winning a point on serve, so any leverage number comes with that assumption. There's no sourced figure here for how often games reach deuce or how many points a match takes. The origin stories are folklore, not history.

Sources

ITF Rules of Tennis
Wikipedia: "Tennis scoring system"
Mental Floss: "Where did tennis get its scoring system?"
Jeff Sackmann, Heavy Topspin: on leverage

Know the gameHow a tennis tiebreak works, and who serves whenA tennis tiebreak is played at 6–6 and won by the first player to 7 points with a two-point lead. One player serves the first point, then serve alternates every two points, 1-2-2-2, and players change ends every six points. A match tiebreak works the same way but goes to 10. Since 2022, all four Slams use it at 6–6 in the final set.MindHow to play big points in tennisPlay big points by taking less risk, not more. The score tells you which points matter: break points, set points, tiebreak points and 15–30. On those, serve to the body or a proven target, hit into the bigger part of the court and run a pattern you've rehearsed. By one estimate, an average tour break point swings match-win probability by about ten percentage points.Know the gameWhat makes a big point in tennis: win probability and leverageTennis win probability is each player's live chance of winning the match, computed from the score and how often each wins points on serve. Leverage is how much one point moves that chance, and it's what makes a big point. A 30–40 break point at 5–6 in a deciding set carries huge leverage. 40–0 at 3–0 carries almost none.Know the gameTennis rules explained: let, fault, foot fault and hindranceYes. A serve that clips the net cord and still lands in the correct box is a let, and the serve is replayed with no penalty. If it clips the net and lands out, it's a fault. Without an umpire, The Code applies: call only your own side, give your opponent the benefit of the doubt, and announce the score before each serve.