The baseline is the back boundary line at each end of a tennis court. It sets the court’s length, marks where a player must stand to serve, and gives players a key reference point during rallies. Knowing how it works can help you call balls more confidently, avoid foot faults, and choose better court positions.
If you’re checking a court at a local park or club, the baseline is also a useful place to start: it helps you spot the net’s center, locate the service boxes, and see whether the court’s lines look correctly laid out. Here’s what to know about its size, rules, and role in play.
What is the tennis court baseline?
The baseline is the line at the back of each side of the court. The two baselines are parallel to the net and 78 feet apart, measured from the outside edge of one baseline to the outside edge of the other. The baseline itself forms part of the court: if the ball touches any part of the line, it is in.
Baselines run across the full width of the court, so they are 36 feet long on a standard doubles court. Singles play uses narrower sidelines, but the baseline does not get shorter. The extra width is used for the doubles alleys.
| Court feature | Standard measurement |
|---|---|
| Court length | 78 feet |
| Court width for singles | 27 feet |
| Court width for doubles | 36 feet |
| Baseline to net | 39 feet |
| Baseline to service line | 18 feet |
Line widths can vary within the rules. Most court lines are 1 to 2 inches wide, while a baseline may be up to 4 inches wide. For close calls, the ball touching the painted line counts as in, even if only a small part of the ball appears to make contact.
How to find the baseline on a local court
Look for the two long lines at the far ends of the playing area. Each one runs parallel to the net and crosses the singles and doubles sidelines. The baseline is usually easy to identify because it is wider than the other lines.
A short center mark divides each baseline in half. It points into the court and helps the server choose the correct side to serve from. The mark is not a separate boundary; it is a guide for serving position.
To check the layout at a park or club, stand near the baseline and look toward the net. The service line should be 18 feet ahead of you, and the net should be another 21 feet beyond that. If you’re unsure which lines apply, the inner sidelines mark the singles court. The outer sidelines and the spaces between them—the doubles alleys—are used in doubles.
Baseline rules for serving
When serving, a player must stand behind the baseline. Before the racket hits the ball, the server cannot touch the baseline, the court inside it, or the area outside the relevant sideline extensions. Stepping on or over the baseline too early is a foot fault.
The server also has to begin each point from the correct side of the center mark. The first point of a game is served from the right half of the court; the next is served from the left. Players switch sides after every point until the game ends.
A practical way to avoid a foot fault is to set your feet behind the line before starting your service motion. Many players stand close to the baseline to use their height and reach, but there’s no rule saying you must serve from right beside it. If you’re learning, leave a little space and focus on a balanced, repeatable motion.
Why the baseline matters in rallies
Baseline position shapes how a point is played. A player who stands close to the baseline can take the ball early and put pressure on an opponent, but has less time to react to a deep shot. Standing farther back gives more room to handle pace and bounce, though it may leave the player open to short angles.
There’s no single ideal position. On a slow, high-bouncing court, a player may need to retreat to handle heavy topspin. On a faster surface, taking the ball near the baseline can keep an opponent from settling into a rally. Even a small adjustment can matter: moving a step back against a strong server may make the return easier, while moving forward against a short second serve can help you attack.
During a rally, the baseline is also a useful visual reference. If you’re pushed behind it, aim for a deep, high-margin shot to regain court position. If your opponent is well behind the line, a shorter ball or angled shot may draw them forward. Players such as Rafael Nadal have built their games around using depth and spin from behind the baseline, while aggressive baseliners often look to step in and take time away.
Calling balls near the baseline
On an unofficiated court, make calls on your own side of the net. If a ball lands close to your baseline, watch where it bounces rather than judging from where it appears to pass in the air. A ball that clips the line is in; one that lands completely beyond the outside edge is out.
When a call is difficult, make it promptly and clearly. If you’re not certain a ball was out, the fair call is in. On courts with electronic line-calling or an official, follow the system or official’s decision.
Frequently Asked Questions
Is the baseline considered in or out?
The baseline is in. A ball that touches any part of it is good, whether it happens during a rally or on a serve.
How far is the baseline from the net?
Each baseline is 39 feet from the net. The full court is 78 feet long, with the net at the midpoint.
Can you stand on the baseline when serving?
You can stand close to it, but you must not touch the baseline or the court beyond it before the racket makes contact with the ball. Doing so is a foot fault.
Does singles use a shorter baseline?
No. The baseline is the same length for singles and doubles. Singles uses the narrower inner sidelines, while doubles includes the wider alleys.
Final Thoughts
The baseline is more than the back edge of a tennis court. It defines the court’s length, helps position the server, and acts as a tactical reference during rallies. When you visit a local court, look for the wide back line and center mark, then use the service line and net to get your bearings. Once you know the layout, the rules and court positions are much easier to read.
