A regulation tennis court line is usually between 1 and 2 inches wide (2.5 to 5 cm). The baseline is the exception: it may be as wide as 4 inches (10 cm). These limits help keep court markings easy to see without changing where the court boundaries are meant to be.
Line thickness matters when you’re checking a local court, repainting a court, or settling a close call. Here’s how official tennis court line widths work, which edges count, and what to look for on a recreational court.
Official Tennis Court Line Thickness
Under International Tennis Federation (ITF) rules, most tennis court lines must be 1 to 2 inches wide. The baseline may be wider, up to 4 inches. The center service line and center mark are specified as 2 inches wide.
| Line marking | Permitted or specified width | Metric equivalent |
|---|---|---|
| Most court lines | 1–2 inches | 2.5–5 cm |
| Baseline | Up to 4 inches | Up to 10 cm |
| Center service line | 2 inches | 5 cm |
| Center mark | 2 inches | 5 cm |
Line widths are measured across the painted or marked strip, not along its length. The rules also require court lines to be a uniform color that contrasts clearly with the playing surface. A line that blends into a hard court or disappears against a clay surface can make calls difficult, even if its width is correct.
Which Edge of a Tennis Line Counts?
A tennis line is part of the area it marks. If any part of the ball touches a line, the ball is in. That applies to the baseline, sidelines, service lines, and the lines around the service boxes.
For a boundary line, the outside edge marks the limit of the court. So a wider baseline does not mean the court suddenly becomes four inches longer: the court dimensions are set by the position of the line’s outside edge. The same principle matters when a court is laid out or repainted. The crew must place the whole line accurately, not simply draw its center over an approximate measurement.
This is why a ball that appears to land on the outer part of a thick line can still be good. On a close call, judge whether any part of the ball touched the line—not whether most of the ball landed inside it.
Does a Thicker Baseline Change Play?
The wider baseline is allowed because it is a prominent marking and often needs to remain visible under frequent foot traffic. It can also be easier to see from the other end of the court. But its width can affect how players read a close bounce: a ball near the edge may look farther inside or outside depending on the viewing angle.
For players, the practical rule is simple: use the outside edge as the boundary. Don’t judge a ball by the middle of a thick line, and don’t assume that a narrow-looking stripe on a worn court is the whole line. If you’re calling your own match, make the call from your side and give your opponent the benefit of the doubt when you can’t be sure.
Checking Line Thickness at a Local Court
Public courts are not always built or maintained to tournament standards. A community court may have faded paint, uneven edges, or markings that are slightly outside the usual range. That does not automatically make it unusable, but clear and consistent lines make casual matches fairer.
- Look for consistent widths. Most lines should appear similar in width, with the baseline potentially wider.
- Check visibility. Lines should stand out from the surface in bright sun and from the far baseline.
- Notice overlaps. On courts marked for both singles and doubles, the different sidelines should be distinct enough to follow.
- Watch for wear. Peeling paint, loose tape, or patchy markings can make a line hard to judge and may create an uneven surface.
If you’re booking a facility for a league match or event, ask whether its courts meet the relevant competition rules. A recreational court can be perfectly fine for a friendly hit while still having markings that differ from a regulation competition court.
Why Accurate Court Lines Matter
Line width is only one part of a correctly marked court. The court’s overall measurements and the placement of each marking matter too. For example, a standard tennis court is 78 feet (23.77 m) long, with a singles playing width of 27 feet (8.23 m) and a doubles width of 36 feet (10.97 m). Correct line placement ensures that the service boxes and playing boundaries match those dimensions.
For players, reliable markings support more than line calls. They help with serving practice, target drills, and judging how much room is available for a crosscourt shot. If a local court’s lines are hard to see, you may find it useful to check them before starting a close match rather than arguing about a bounce later.
Frequently Asked Questions
How thick should tennis court lines be?
Most official tennis court lines should be 1 to 2 inches (2.5 to 5 cm) wide. The baseline can be up to 4 inches (10 cm) wide. The center service line and center mark are 2 inches (5 cm) wide.
Does the ball count as in if it touches the edge of the line?
Yes. A ball is in if any part of it touches the line. This includes the outside part of a thick baseline or sideline.
Does a wider baseline make the tennis court bigger?
No. The court boundary is measured at the outside edge of the baseline. Making the stripe wider does not move that edge if the court has been marked correctly.
Are public tennis courts required to use official line widths?
Competition courts should follow the applicable tennis rules. Public and recreational courts can vary in condition or markings, so check with the facility if you need a court for an organized match.
Final Thoughts
Most tennis court lines are 1 to 2 inches wide, while a baseline may be up to 4 inches. The width is easy to remember, but the key detail for players is that the line counts as part of the court: any contact with it is in. When checking a local court, look for lines that are visible, consistent, and correctly placed—not just freshly painted.
