What choosing wrong costs
Enter too high and every point ends in two shots; you go home feeling you never played tennis at all. Enter too low and you get the same result from the other side: a win without a single point that made you think. Both waste your afternoon and your opponent's.
The right level is where most points run four to eight shots, where you win some games and lose some, and where you come off court feeling you had to decide something the whole way through.
What a level number means
Most events sort players by a number, from about 2.5 for someone who has just learned to rally, up to 4.0 and above for players who control direction, depth and pace at will. The numbers are not an exam. They describe how you usually play, and each event defines them a little differently.
A reading that works almost everywhere: at 2.5 you can rally slowly but not yet steer the ball; at 3.0 you rally at medium pace but miss when the rhythm changes; at 3.5 you start placing the ball where you meant to and own a second serve you trust; at 4.0 and above you can play more than one way and make decisions under pressure.
An honest look at yourself
The most useful question is not how well you hit, but when you miss. If the misses are the balls you had to run for, you are probably lower than you think. If they are the balls you tried to finish with, you are probably a touch higher than you rated yourself.
Another way is to look at the people you play with regularly. If you beat that group nearly every time, try one level above them. If you lose to them nearly every time, their level is the one you are heading for, not the one you are at.
In practice most players rate themselves about half a level high, because the good days are the ones you remember. If you are torn between two levels, enter the lower one for your first match and move up when the results say so.
When there are only two levels
Many small events offer just two levels, beginner and intermediate. A simple rule: if you cannot yet land a second serve every time, or have not played real points regularly, choose beginner. Intermediate at events like these usually contains people who have played for years.
Entering doubles
Doubles uses the same numbers, but you have to think as a pair. Most organisers look at the combined level of the two of you, or cap how high the stronger partner may be. Pairs with a wide gap tend to do worse than pairs who match, because the opponents hit to the weaker player all match long.
If you partner someone stronger, enter at the level the weaker player is comfortable at, not the stronger one's. A good doubles match is one where all four players get to hit the ball, not one where somebody stands and watches.
Signs it is time to move up
The clearest sign is winning the same bracket three or four events running while dropping very few sets, or noticing that points end quickly because the other player misses first, not because you played well. Another is boredom. Getting bored in a bracket that used to be fun usually means your game has outgrown it.
The first move up usually comes with a run of losses. That is normal and it is supposed to happen; a new level takes two or three events before it feels like the right place. If the points are still very short after that, step back down. Nobody remembers who dropped a level; everybody remembers who was fun to play.
Once you have chosen
Give your true level when you enter. The organiser uses that number to pair you and to build the draw. Entering low to win easily costs somebody else their match, and people in the game remember that sort of thing.
After the event, look back at how long the points ran. If they were very short in one direction or the other, adjust by one level next time. A level is not a permanent label; it changes every time you play more.
Rate yourself before you enter
THE SET.'s Court Level is a ten-question self-assessment that places players in sessions where both sides enjoy the match. Sign up and take it straight away, and take it again when your game changes.
General guidance, not a research finding.