Look down the middle of a tennis court and you’ll see a short line running from the net toward the service line. That’s the center service line, and it helps define where a serve must land. It’s easy to confuse it with the small mark at the middle of the baseline, but the two lines have different jobs.
Knowing which line is which makes court markings easier to read, whether you’re setting up a local court, learning the rules, or trying to understand a close serve call. Here’s how the tennis court center line works and what to look for when you step onto the court.
What Is the Tennis Court Center Line?
The center service line is the line that divides the service area into two boxes: the left service court and the right service court. It runs from the net to the service line, meeting that line at its midpoint. On a standard court, it is 21 feet long.
Each service box is 21 feet deep and 13.5 feet wide. Its boundaries are the net, the service line, the center service line, and the singles sideline. Although the center service line may look like a small detail, it is essential for judging whether a serve lands in the correct box.
A serve that touches the center service line is good, as long as it lands in the correct service box and does not touch the net and then land out. In tennis, a ball landing on a boundary line counts as landing inside the area that line defines.
Center Service Line vs. Baseline Center Mark
Players often use “center line” to mean two different markings. The center service line is near the net. The center mark is the short mark at the middle of each baseline. They are not connected by a painted line.
| Marking | Where it is | What it does |
|---|---|---|
| Center service line | Between the net and the service line | Separates the left and right service courts |
| Baseline center mark | At the midpoint of each baseline | Shows where the baseline is divided for serving positions |
The center mark helps the server line up behind the correct half of the court. For each point, the server starts behind the baseline and serves diagonally into the opposite service box. After serving from one side, the server switches sides for the next point. The center mark makes that division easy to spot.
Where the Center Line Sits on a Tennis Court
A standard tennis court is 78 feet long. The service line is 21 feet from the net, and the center service line runs through the middle of the service area. It divides the service boxes evenly, with each box measuring 13.5 feet across between the center service line and the singles sideline.
The service boxes are the same size in singles and doubles. Doubles courts are wider because they include the alleys outside the singles sidelines, but those alleys do not make the service boxes wider. A doubles serve still has to land inside the same service box as a singles serve.
When you’re locating a court’s center line, find the net first, then look toward the service line for the line running down the middle of the service area. For the baseline center mark, look at the midpoint of the baseline behind each player. These markings should line up with the middle of the court and the center of the net.
How Players Use the Center Line
For serving
The center service line is one of the boundaries a serve must land within. A right-handed player serving from the deuce side, for example, aims diagonally into the receiver’s left service box. The ball can land on the service line, singles sideline, or center service line and still be good. If it lands beyond those boundaries, it is a fault.
At a local court, line wear can make a close call tricky. If the center service line is faded, watch where the ball first hits rather than where it skids or bounces next. Players should make calls promptly and give the benefit of doubt to their opponent when they cannot clearly see the landing.
For court positioning
The center mark helps a server judge where to stand behind the baseline. It also gives players a useful visual reference when they return serve or recover after a shot. After hitting wide, many players move back toward the middle of the court—not always directly over the center mark, but toward a position that covers the opponent’s likely replies.
The center service line can also help players picture their angles. Aiming down the middle of the service box often gives a server a larger margin than trying to hit close to a sideline. It may also reduce the receiver’s ability to pull the return sharply crosscourt.
Checking Center Lines at a Local Court
Before you play, take a moment to check that the center service line and baseline center marks are visible. Outdoor courts can collect dirt, leaves, or sand across the lines, while older painted markings may fade. On clay, lines may be raised or made from strips; on hard courts, they are usually painted onto the surface.
- Confirm the court layout: The center service line should meet the middle of the service line.
- Look for uneven or faded paint: Poor visibility can lead to disputes on serves.
- Keep temporary lines clear: If a facility uses blended court markings, check which lines belong to the court you booked.
- Use the center mark as a reference: It should sit at the midpoint of the baseline, not off to one side.
If a court has a missing or badly misplaced marking, ask the facility before play rather than trying to guess during a match. On a properly marked court, the service line, center service line, and singles sidelines make the service boxes clear from both ends.
Frequently Asked Questions
Is the center service line in or out?
It is in when a serve lands on it, provided the ball is inside the correct service box. Boundary lines count as part of the area they mark.
Does the center line continue across the net?
No. The center service line runs only between the net and the service line. The court’s midpoint is also indicated by the baseline center marks, but there is no painted line connecting them.
Do singles and doubles courts have different service boxes?
No. The service boxes have the same dimensions in singles and doubles. Doubles courts add width outside the singles sidelines, but the extra alleys are not part of the service boxes.
What is the small mark in the middle of the baseline for?
It is the baseline center mark. It helps show the midpoint of the baseline and gives the server a clear reference for serving from the correct side.
Final Thoughts
The tennis court center line is the center service line: the marking that splits the service area into two boxes. It sets a boundary for serves, while the small mark at the baseline helps players identify the court’s midpoint. Once you know the difference, court markings—and close serve calls—are much easier to understand.
