What Do Tennis Court Lines Mean?

The first time someone shows up on the tennis court, they might not understand what all the lines mean. It can seem not very clear at first, as tennis is not the easiest sport in the world to earn.

We go over the basics below concerning what the tennis lines mean on a traditional court. By knowing this information, it becomes a lot less complicated to go out there and play the game at any court. While some courts might be a bit more cluttered with other lines, knowing the tennis-specific lines make a difference.


The baseline on a tennis court is 39 feet away from that net on either side. The length of the court does not change, regardless of it being a singles or doubles match.

It is usually a very thick line at the baseline, and the starting line for the server beginning each point. Servers must stay behind this baseline when they make contact with the serve, but they can step over or back behind it at any point after.

Singles Sideline

There are two singles sidelines on each side of the court, and they are 27 feet apart. This is the distance that a player must cover when they are playing singles.

They are the interior lines on a traditional court, as the singles sidelines make the court smaller in surface area than the doubles court.

Doubles Sideline

The length of a tennis court is the exact same for single and doubles, but the width is where things get a little bit different. There are doubles alleys on each side of the court, and they are 4.5 feet in width each. This means that the total width of a doubles court is 36 feet, compared to 27 feet for singles.

This extra amount of space offers up an opportunity for players to hit wider angles and have a bit more leeway with their shots.

Since there are two players on each side of the net, it’s easier to cover more area. Generally speaking, doubles matches need a little bit more extra amounts of room on the sidelines to cover some of the angles.

Service Box

At the start of each point, the server must hit the ball into the diagonally-placed service box on the opponent’s side. The service box is defined by a service line, which is 21 feet from each side of the net. This means that it is a little bit closer to the baseline than the net, as there are just 18 feet between the service line and the baseline.

The service box does not change in size for singles and doubles. Both types of play require the server to hit a ball into the box that is 13.5 feet wide, and 21 feet long. The ball can hit any part of the box (or lines) to be a valid serve.

Center Mark

There is a small center mark drawn on the baseline to help with serves. For a server, they must stay on one side of that mark when they are serving to the diagonal side of the court. No part of the feet can pass that center mark, or else it is a fault.


The net doesn’t officially have a line, but it’s still important to understand some of the basics of the net. For starters, a player can not come in contact with a net during the point. By doing so, that player automatically loses the point. This even includes taking a swing at a ball and hitting a winner, but during the finishing of the swing, the racquet hits the net.

Another thing to keep in mind is that there is an imaginary line where the net stands. The only time a player can make contact with a ball over the net is if it already bounced on their side of the court.

For example, this can happen when there is a lot of backspin on a ball, and it kicks off one side of the court and goes back over. This is when a player can reach over, hit the ball for an attempt at a winner, and then come back to their side.

If they do not make contact with the ball to finish off the point, it is a winner for the player who hit it (despite the ball bouncing back over).

If The Ball Hits a Line – In or Out?

Even if the ball only touches a tiny bit of the outside part of the line, it’s considered in. It can be nearly impossible to call a close ball in or out, especially at the highest level. The good news is that there is a lot more replay opportunities for shots that are close, and it happens fast enough that players get an answer quickly.

In many sports, a ball that hits the line is considered out. That’s why there might be some confusion as to whether or not a ball that hits the line is good or not. Another thing that causes confusion is that the ball compresses a lot when it goes up against the ground.

That’s why it might not seem like it actually hit the line at first glance, but it actually did. To better get an understanding of that, playing on clay courts is an excellent learning opportunity. The ball leaves distinct marks on the clay court, showing just how weirdly the ball makes contact with the ground at times.

What Are All These Other Lines For?

Some multipurpose courts will have other lines on them beyond what is mentioned above. This can be very confusing for tennis players, but they don’t need to pay attention to them. They are most likely either for pickleball, or junior tennis.

The good thing is that in most cases, those in charge of developing courts are using different colors for those lines. It’s very easy to be distracted about them at first, but since the tennis lines are pretty simple, most adjust.

Understanding Lines Makes For Easier Playing

Tennis players just starting out can sometimes feel intimidated, but the lines for tennis are pretty easy to get the hang of.

The most confusing parts include serving, and figuring out if a ball actually hit a line or not. It is hard to mess up the dimensions of a tennis court, which is good news for those heading to public parks.

Fred Simonsson

I'm Fred, the guy behind TennisPredict. Apart from writing here, I play tennis on a semi-professional level and coach upcoming talents.

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