A point ends and two people disagree: was that ball out? Or you are planning a court at home, a club extension or a school playground and need the numbers before anyone orders paint. Either way the question is the same: how big is a tennis court, exactly, and what is each line for?
This guide gives the standard measurements in metres and feet, explains the lines, and covers the part most diagrams skip: the empty space around the court. The playing-area figures come from the International Tennis Federation (ITF) Rules of Tennis. For the space beyond the lines I rely on a secondary summary and say so, because the rulebook is less specific there.
The short answer: the numbers that matter
| Measurement | Feet | Metres |
|---|---|---|
| Court length (baseline to baseline) | 78 ft | 23.77 m |
| Doubles width | 36 ft | 10.97 m |
| Singles width | 27 ft | 8.23 m |
| Service line to net | 21 ft | 6.40 m |
| Service line to baseline | 18 ft | 5.49 m |
| Doubles alley (each side) | 4.5 ft | 1.37 m |
| Net height at the posts | 3 ft 6 in | 1.07 m |
| Net height at the centre | 3 ft | 0.914 m |
Length and the two widths are in Rule 1 of the ITF Rules of Tennis. The service line sits 21 feet from the net. The remaining rows are arithmetic: the net is at the halfway point, 39 feet from each baseline, so the strip between the service line and the baseline is 39 − 21 = 18 feet. Each alley is (36 − 27) ÷ 2 = 4.5 feet.
If you remember one thing: the court is the same length for singles and doubles; only the width changes.
Singles vs doubles court size
The full rectangle, 78 by 36 feet, is the doubles court. The singles court sits inside it, 27 feet wide, leaving a 4.5-foot alley along each side.
- Singles: the inner sideline counts. A ball landing in the alley is out.
- Doubles: the outer sideline counts, so the alleys are in play during rallies. A serve still has to land in the correct service box, which is bounded by the singles lines.
For serving order and positions in doubles, see our tennis doubles rules guide, which also covers the usual alley arguments.
Why the alleys exist
Two players per side cover more width, so doubles uses a wider court and rewards angles and net play. Singles keeps the narrower court so one player can cover it. It is one surface with two sets of lines.
The lines, one by one
Baseline
The back line, 78 feet from the opposite baseline. A ball landing beyond it is out, and the serve is hit from behind it.
Sidelines
Two pairs: singles (inner) and doubles (outer). Which pair counts depends on the match.
Service line and service boxes
The service line runs parallel to the net, 21 feet (6.40 m) away. The centre service line splits the area between the service lines and the net into two boxes. Each box is 21 feet deep and 13.5 feet wide (half of the 27-foot singles width). A serve must land in the diagonally opposite box.
Centre mark and centre service line
The centre mark is a short line at the middle of each baseline; it tells the server which side they must stay on. The centre service line divides the two service boxes. I am not quoting exact line thicknesses as rule: an Asics guide describing the ITF rules gives the centre service line as about 5 cm wide and other lines as between 2.5 cm and 5 cm, but I could not confirm that against the rulebook text. Check Rule 1 if you are marking a court.
The strip behind the service line
Players call the zone between the service line and the baseline “no man’s land”. It is 18 feet deep, a good reminder of how much of the court a short ball leaves open.
The net: height and posts
The net hangs from a cord or cable over two posts. The ITF rule:
- 3 ft 6 in (1.07 m) at the posts
- 3 ft (0.914 m) at the centre, held down tightly by a strap
For doubles, the centre of each post sits 3 feet (0.914 m) outside the doubles sideline. Posts may be no more than 6 inches (15 cm) square or round, and the posts and singles sticks may not stand more than 1 inch (2.5 cm) above the top of the net cord. When a doubles-width net is used for singles, singles sticks mark the singles sideline.
Run-off: the space around the court
Lines painted right up against a fence make a court nobody enjoys. Players need room to chase balls past the baseline and wide of the sidelines. The rulebook sets the markings; the space around them depends on the level of play and on the facility design.
A Tennis Australia dimensions summary, which cites ITF technical guidance, lists these figures:
| Level | Behind the baseline | Beside the sideline |
|---|---|---|
| Club / recreational | about 5.49 m | about 3.05 m |
| International minimum | about 6.40 m | about 3.66 m |
| International preferred | about 8.23 m | about 4.57 m |
Other sources round the club back run-off to 5.48 m, so treat these as design guidance, not law. They are not a requirement for a friendly game.
What that adds up to
For a club-standard court, a doubles court plus run-off is about 34.75 m by 17.07 m (23.77 + 2 × 5.49 and 10.97 + 2 × 3.05), roughly 593 square metres. That is my own arithmetic from the figures above. Courts built side by side often share side space, so the footprint per court in a block can be smaller. Confirm with your contractor or national association.
Courts that do not follow the textbook
Many courts, particularly in hotels, condos and city rooftops, are fitted into whatever space exists. Run-off may be tight and the fence close. The lines themselves are usually standard, so judge a court by its markings first.
How the lines decide points
Dimensions matter most when a ball lands near a line. Three rules cover most arguments:
- A ball that touches a line is good. Every line belongs to the area it bounds, so a ball clipping the baseline, a sideline or a service line is in. This is why line widths matter: a ball only has to touch the edge of the paint.
- The serve is judged against the service box, not the whole court. A serve that lands in the alley, long or in the wrong box is a fault, even if it would have been in during a rally.
- The singles and doubles lines are used by match type. In doubles, a serve is hit into the same service boxes as in singles (the singles lines bound them), but rallies use the full 36-foot width.
Most recreational disputes come from the second and third points rather than from the distances themselves. If you play doubles regularly, the tennis doubles rules guide walks through them, and our guide to tennis scoring covers what happens once the point is decided.
Playing on a court with several sets of lines
Some multi-use courts, such as school halls and community courts, carry pickleball, badminton or padel lines over the tennis markings. The tennis lines are the longest, usually in a distinct colour; if you cannot tell which is which, measure the baseline-to-baseline distance (23.77 m) and the net-to-service-line distance (6.40 m) with a tape before you play for points.
If you are building or booking a court
Two questions are worth asking any venue. First, are the markings standard, meaning the full 23.77 m by 10.97 m with a 6.40 m service line? Second, how much run-off is there behind the baselines? A court that meets the first but not the second is still playable, but you will notice it when you chase a lob. For travellers, the venue’s own site or a message to the front desk is the only reliable way to find out, since directories rarely list run-off. Our court directory lists courts by city, but check the details with the venue.
Surface does not change the size
Hard, clay, grass and indoor courts share the same playing dimensions. What changes is speed, bounce and how the lines are made. A court in Bangkok has the same markings as one anywhere else.
Shorter courts and lower nets exist for young players under the ITF’s junior formats. Figures vary by stage and national association, so I do not give them here; take them from your association’s current guidance.
Quick checks for your own court
- Measure the length first: 23.77 m between the baselines.
- Check the diagonal: a 23.77 m by 10.97 m rectangle has a diagonal of about 26.18 m (the square root of 23.77² + 10.97²). Equal diagonals mean square corners.
- Mark the service line 6.40 m from the net, not from the baseline.
- Check the net at the posts (1.07 m) and the centre (0.914 m).
- Leave run-off before placing fences.
Putting the numbers to use
Dimensions make line calls and shot choices more honest. A ball that lands just past the service line still has 18 feet to run, so it is not as deep as it feels. A doubles passing shot is good if it lands inside the outer line. And when you play on a new court abroad, you know what the lines should look like.
If you would rather get on court than measure one, Breakers runs Open Play: level-matched, drop-in social tennis sessions where you book a seat for your level and play with people at a similar standard, no partner needed. It runs in Bangkok for now. To find a court anywhere else, browse the court directory. The scoring that goes with these lines is in our guide to how tennis scoring works, and if you are new to the game, start with the beginner guide.
Sources
- ITF, Rules of Tennis 2026 (Rule 1, The Court; net and posts) — https://www.itftennis.com/media/7221/2026-rules-of-tennis-english.pdf
- Tennis Australia, court dimensions and run-offs summary — https://www.tennis.com.au/sa/files/2023/07/Dimensions.pdf
- Asics, Tennis court dimensions guide (line widths, secondary source) — https://www.asics.com/de/en-de/asics-advice/tennis-court-dimensions/
Frequently asked questions
How big is a tennis court?
A doubles court is 78 feet long by 36 feet wide (23.77 m by 10.97 m). A singles court uses the same length but is 27 feet (8.23 m) wide. Both sets of lines are normally painted on the same surface.
What is the difference between a singles and a doubles court?
Only the width. The two side strips between the singles and doubles sidelines, called the alleys, are 4.5 feet (1.37 m) wide each. They are in play in doubles and out in singles.
How high is a tennis net?
The ITF Rules of Tennis give 3 feet 6 inches (1.07 m) at the posts and 3 feet (0.914 m) at the centre, where a strap holds the net down.
How much space do you need around a tennis court?
The ITF rules set the court markings, not a single run-off figure for every game. A Tennis Australia dimensions summary based on ITF technical guidance lists about 5.49 m behind the baseline and 3.05 m at the sides for club courts, with more for international level. Treat these as design guidance and check with whoever builds or manages the court.
How far is the service line from the net?
21 feet (6.40 m). The service boxes are therefore 21 feet deep, and the strip between the service line and the baseline is 18 feet (5.49 m).
