A full-size tennis court is 78 feet long.

The governing rule and version used here

This page applies the ITF 2026 Rules of Tennis, principally Rules 1, 2, 12, 13 and 16–19 and Appendices VIII–X. The ITF is the international governing body and custodian of the Rules of Tennis. Alterations normally take effect on 1 January following approval; the 2026 edition is therefore the effective baseline from 1 January 2026.

The dimensions below are for conventional full-size tennis. ITF 10-and-under competition has authorised Red and Orange courts, covered separately below. Beach tennis, padel and pickleball have different rules. Tournament regulations may add surface, clearance, lighting or venue requirements without changing which painted line bounds a standard point.

Length stays fixed; singles and doubles use different widths

ITF Rule 1 makes the court a 78-foot (23.77 m) rectangle from the outside edge of one baseline to the outside edge of the other. The net divides that length equally, leaving 39 feet (11.89 m) from the net to each baseline.

• Singles: 27 feet (8.23 m) between the outside edges of the singles sidelines.
• Doubles: 36 feet (10.97 m) between the outside edges of the doubles sidelines.
• Each doubles alley: 4 feet 6 inches (1.37 m) between the singles and doubles sideline.

Most courts carry both sets of sidelines. The paint does not decide the format; the match format decides which sideline is the boundary.

What each line controls

• Baselines close both ends of the court and form the server's near boundary.
• Singles sidelines form the side boundaries in singles and also the outside boundaries of every service court.
• Doubles sidelines replace the singles sidelines only for doubles rallies.
• Servicelines run between the singles sidelines, parallel to and 21 feet (6.40 m) from the net.
• Centre serviceline divides the area between each serviceline and the net into the right and left service courts.
• Centre mark is 4 inches (10 cm) long, lies inside each baseline and divides the two service positions.

The visible court is not always the playable court

In singles, the inner sidelines are the rally boundaries and both alleys are out. In doubles, the outer sidelines bound returns and later rally shots.

The service target is identical in width in singles and doubles. Rule 1 draws each serviceline only between the singles sidelines, and Rule 17 requires the serve to hit the diagonally opposite service court. A serve in the doubles alley is therefore a fault even during a doubles match.

The centre mark and sideline have imaginary extensions

Immediately before the service motion, Rule 16 requires the server to stand at rest with both feet behind the baseline and between the imaginary extensions of the centre mark and the applicable sideline. Rule 18 then prohibits either foot from touching the baseline, the court, the centre-mark extension or the area beyond the sideline extension during the service motion.

The 2026 amendment clarifies an important format difference: in singles, the server may not stand behind the alley between the singles and doubles sidelines. In doubles, that position is permitted because the doubles sideline is the applicable outer limit. This changes the available serving position, not the width of the diagonal service target.

A line is in only when it bounds the relevant target

ITF Rule 12 says a ball touching a line is regarded as touching the court bounded by that line. A rally ball clipping the applicable baseline or sideline is in. A serve clipping the correct serviceline, centre serviceline or singles sideline is also in, subject to the other service rules.

The word applicable matters. A singles rally ball can touch the doubles sideline and still be out because that line does not bound the singles court. Likewise, the doubles sideline does not bound a service court. For practical calling procedures, see line calls and hindrance.

Width and measurement are controlled by Rule 1

All court dimensions are measured to the outside of the lines. The centre serviceline and centre mark must be 2 inches (5 cm) wide. Other lines must be between 1 inch (2.5 cm) and 2 inches (5 cm), except that a baseline may be as wide as 4 inches (10 cm).

All lines must be the same colour and clearly contrast with the surface. Appendix X also permits sanctioning bodies to approve “blended lines” for smaller-court formats, but prescribes their colour, pace, width and termination relative to the standard lines. Extra markings are therefore not automatically authorised playing lines.

The centre is lower than the supports

Under Rule 1, the net is 3 feet 6 inches (1.07 m) high at the posts or singles sticks and 3 feet (0.914 m) at the centre, where a completely white strap holds it down. The net must fill the space between its posts and have mesh small enough that the ball cannot pass through.

• Doubles net: each post centre is 3 feet (0.914 m) outside the doubles sideline.
• Dedicated singles net: each post centre is 3 feet outside the singles sideline.
• Singles on a doubles net: two singles sticks must support the net 3 feet outside the singles sideline on each side.

Outer posts change status in singles

Rule 2 classifies backstops, sidestops, spectators, stands, court furniture and officials or ball persons in their recognised positions as permanent fixtures. In singles played with a doubles net and singles sticks, the doubles net posts and the net outside the sticks are also permanent fixtures; they are not treated as part of the playable net.

Timing decides the outcome under Rule 13. If a ball in play hits a permanent fixture after first landing in the correct court, the striker wins the point. If it hits the fixture before a bounce, the striker loses the point. A served ball touching a singles stick or net post before landing is specifically a service fault under Rule 19.

The playing enclosure is larger than the court

The 78-by-27-foot or 78-by-36-foot rectangle is the court, not the whole space a player may use. ITF Appendix X recommends, as minimum guidance for international competition, 21 feet (6.40 m) between each baseline and backstop and 12 feet (3.66 m) between each sideline and sidestop.

For recreational and club play, Appendix X recommends 18 feet (5.48 m) behind each baseline and 10 feet (3.05 m) beyond each sideline. It also recommends 29.6 feet (9.0 m) of ceiling height measured at the net. These are ITF guidance figures, not extensions of the in-bounds court. An appointed competition or venue may impose additional facility standards.

Red and Orange courts are authorised exceptions

ITF 2026 Appendix VIII expressly permits smaller courts for 10-and-under competition:

• Red court: 36–42 feet (10.97–12.80 m) long, 14–20 feet (4.27–6.10 m) wide, with the net 31.5–33 inches (0.800–0.838 m) high at the centre.
• Orange court: 58–60 feet (17.68–18.29 m) long, 20–27 feet (6.10–8.23 m) wide, with the net 31.5–36 inches (0.800–0.914 m) high at the centre.
• Green-ball competition: uses the full-size court.

These are ruleset-authorised formats, not evidence that a full-size adult court may be resized by local preference.

A doubles serve lands in the alley

Situation: the server stands legally behind the doubles alley and serves diagonally. The ball clears the net but first bounces between the singles and doubles sidelines.

ITF 2026 ruling: service fault under Rules 17 and 19. Doubles permits the wider serving position, but the doubles alley is not part of either service court.

A serve clips the centre serviceline

Situation: the ball first lands partly on the centre serviceline of the correct diagonal service court.

ITF 2026 ruling: the serve is in under Rule 12, provided no other fault occurred. The centre serviceline bounds both adjacent service courts, so touching it counts as touching the correct court.

A singles rally ball clips the outer sideline

Situation: on a court marked for both formats, a singles rally ball misses the singles sideline but touches the doubles sideline.

ITF 2026 ruling: out. Rule 12 saves a ball only when it touches a line bounding the relevant court. The doubles sideline does not bound a singles match.

The ball strikes an outer net post in singles

Situation: singles is played with a doubles net and correctly placed singles sticks. A rally shot hits an outer doubles net post before bouncing.

ITF 2026 ruling: the striker loses the point under Rules 2 and 13. In this setup the outer post is a permanent fixture, and the ball hit it before landing in the correct court. If the ball had first landed in the correct court and then hit that fixture, the striker would win the point.

How to judge a court-boundary question

1. Name the format. Singles, doubles and ITF 10-and-under formats do not use the same outer boundaries.
2. Name the shot. A serve targets one diagonal service court; a rally ball targets the full applicable court.
3. Select the controlling line. Ignore painted lines that do not bound that format and shot.
4. Check contact. Any touch of the controlling line is in under Rule 12.
5. Check the net setup. In singles on a doubles net, identify the singles sticks and which parts are permanent fixtures.
6. Separate court from enclosure. Run-off and ceiling guidance affect facilities, not the in-bounds rectangle.

Claims the 2026 rules do not support

• “The doubles alley is always in.” It is in for doubles rallies, out in singles and outside the service courts in both formats.
• “Every painted line can make a ball good.” Only a line bounding the relevant court or service target matters.
• “A wider baseline makes the court longer.” Rule 1 measures the court to the outside edges and controls permitted line widths.
• “The net is 3 feet high everywhere.” It is 3 feet at the centre and 3 feet 6 inches at its supports.
• “The fence is the boundary.” Fences and backstops are permanent fixtures outside the marked court.
• “Every junior match uses a smaller court.” Appendix VIII assigns Red and Orange formats specific ranges; Green-ball competition uses the full-size court.

Facility defects are not given one universal match remedy

Rule 1 and Appendices IX–X state how a compliant court is laid out. They do not prescribe one automatic score or replay outcome for every late-discovered faded line, misplaced stick or facility defect. The referee or competition authority must apply the event's procedures and decide whether the court can be corrected or play can continue safely.

That administrative decision is separate from an ordinary line call. When the markings are compliant and visible, officials first select the line that bounds the particular format and shot, then apply Rule 12.

Governing-body sources and effective version

• International Tennis Federation — 2026 Rules of Tennis, Rules 1–2, 12–13 and 16–19; Appendices VIII–X
• International Tennis Federation — 2026 Amendments to the Rules of Tennis, Rule 18 foot-fault clarification

Checked on 28 August 2026 against the ITF 2026 English rulebook and the separately published 2026 amendments, effective from 1 January 2026. The ITF baseline controls the court and markings discussed here; an appointed competition's current regulations may add venue standards or an approved trial.