BaselineThe rearmost line at each end of the court. It runs parallel to the net. The server starts behind it, between the center mark and the sideline.
Service lineThe line that marks the back of the service boxes. Parallel to the net, 21 ft (6.4 m) from it.
Center service lineDivides the two service boxes of each side. It runs from the net to the service line.
Singles sidelineThe inner side line on each side. In singles the court is 27 ft (8.23 m) wide, out to these lines.
Doubles sidelineThe outer side line on each side. In doubles the court is 36 ft (10.97 m) wide, out to these lines.
NetRuns across the middle. It is 3 ft 6 in (1.07 m) high at the posts, 3 ft (0.914 m) in the center.
The areas: 3 3
AlleyThe strip between the singles and doubles sidelines on each side. Used only in doubles. In Britain it is the tramlines.
Service boxesA serve must land in the box diagonally opposite. The four boxes are bounded by the net, the service line, the singles sideline and the center service line.
Back courtThe area from service line to baseline at each end.
Marks and posts: 3 3
Center markThe short 4-inch mark at the middle of each baseline. It divides the court into halves for serving.
TThe T shape where the center service line meets the service line.
Net postsHold the net up at each end. They stand just outside the court.
How this list was compiled: Read 2026-09-27. Wikipedia, Tennis court, https://en.wikipedia.org/wiki/Tennis_court (citing the ITF Rules of Tennis, rule 1, The Court): the court is 78 ft long, 27 ft wide for singles and 36 ft for doubles; the net divides it into two equal ends, 3 ft 6 in high at the posts and 3 ft in the centre; the service line is 21 ft from the net; terminology: the alley or tramlines (only used in doubles), back court, baseline, center service line, center mark (the 4-inch mark in the middle of the baseline), service box (bounded by the singles sideline, service line and net), service line, and the T. Wikipedia, Tennis, https://en.wikipedia.org/wiki/Tennis : the serve is hit into the diagonally opposite service box; the server stands behind the baseline, from the centre mark to the sideline. Licence: own work
The drawing: Drawn for this site by script, 2026-09-27. Own work, nothing traced. Licence: own work
How it works
A tennis court diagram labeled from above, drawn to the proportions in the rules: 78 ft long, 36 ft wide for doubles. Start with the 6 main parts.
Read the full guide
The lines
The baseline runs across each end, with the center mark in its middle. The service line crosses each half 21 ft from the net, and the center service line splits the space in front of it into two service boxes.
Singles and doubles
The singles sidelines make the court 27 ft wide. In doubles the court widens to the outer doubles sidelines, 36 ft apart, adding the alley down each side.
A serve must land in the service box diagonally opposite, so the center mark and center service line decide which side you serve from.
Questions and answers
What are the lines on a tennis court called?
The baseline across each end, the service line, the center service line, the center mark, and the singles and doubles sidelines down each side.
What is the alley in tennis?
The strip down each side between the singles and doubles sidelines. It is only in play in doubles; in Britain it is called the tramlines.
How big is a tennis court?
78 ft (23.77 m) long, and 27 ft (8.23 m) wide for singles or 36 ft (10.97 m) wide for doubles. The net is 3 ft high in the centre.