You’re up 40-0, feeling good, and then you wonder: why on earth do we count points like this? 15, 30, 40, game. It’s one of those quirks that makes tennis instantly recognisable, but its origin is surprisingly murky. Let’s sift through the theories and land on the most likely explanation.

The medieval clock theory

The most popular story goes like this: in the Middle Ages, a clock face was used to keep score. Each point moved the hand a quarter of the way round: 15 minutes, 30 minutes, 45 minutes, and then the hour (game). Over time, the 45 was shortened to 40 for convenience—less of a mouthful, easier to say quickly between rallies.

It’s a neat image, and many tennis histories repeat it. The problem? No solid evidence. There’s no medieval rulebook or illustration showing a clock on court. And why would you shout “40” instead of “45”? That’s a pretty early abbreviation for a game that prides itself on tradition. Still, the clock theory persists because it’s memorable.

The betting theory

Another idea: scoring came from the French game jeu de paume, the ancestor of tennis. In the 15th century, a common bet was 15 sous per point. The game was played to 60 sous (four points). So you’d win 15, then 30, then 45, then 60 for the game. Again, the 45 became 40 over time.

This theory has the charm of linking scoring to money—always a plausible motive. But again, hard proof is thin. The first written mention of tennis scoring (from around 1500) says “15, 30, 45” but not “40”. So the shift to 40 happened later, and we don’t know exactly why.

The honest answer: we don’t really know

Historians generally agree that the scoring system originated in France in the 13th or 14th century. The earliest known reference to tennis (or jeu de paume) scoring is in a 1431 poem by Charles d’Orléans, where a game is described as “quinze” (15), “trente” (30), “quarante” (40). So the 40 was already there by then.

The most plausible explanation is that the numbers simply represented a convenient way to divide 60—a common base in medieval counting. Think of a circle: 360 degrees, or 60 minutes on a clock. Four points add up to 60, so each point is 15. The third point, 45, was perhaps shortened to 40 because it sounded better or was easier in French (“quarante” vs “quarante-cinq”). No deep reason—just a linguistic convenience.

Why it still matters

Even without a clear origin, the 15-30-40 system has stuck for over 500 years. It’s a beautiful example of how tradition can outlast logic. Today, every player uses it without a second thought, and it gives tennis a unique rhythm. The pause between 30 and 40, the tension of deuce, the sudden release of game—all built on a counting system that probably started as a simple fraction of 60.

Next time you’re down 15-40, remember: you’re part of a centuries-old mystery. And honestly, that’s part of the fun.

Take it to court

• Embrace the quirk: Don’t waste energy wondering why—use the scoring rhythm to your advantage. The pause at 40-30 can be a moment to reset.
• Know the history, but don’t overthink it: Understanding where scoring comes from might help you respect the game’s depth, but on court, focus on the point, not the number.
• Have an answer ready: When a curious friend asks “Why 40?”, you can now say: “Nobody knows for sure, but it’s probably because 45 was too long to say in French.” That’s a cool fact to share.

Remember: the score is just a way to keep track. The real game is in the shots you play.