When Is A Ball Out In Tennis? (Tennis Instructor Explains)

One of the most common questions I get as a tennis instructor from beginning players is: when is the ball out in tennis?. Of course, this is also one of the basic rules you need to know. So with this article, I hope to answer all your questions on this topic!

In tennis, a ball is out when it lands outside the lines of the court. Which lines are in or out at that moment may vary by match type or game situation. If a ball touches the line in question, even minimally, it is counted as in.

Tennis is a complex sport with a ton of complicated rules. So, in this article, we'll dive into the nuanced rules and etiquette of calling a ball in or out.

What Counts as Out in Tennis?

As you probably know, a tennis court consists of several lines. These lines determine the playing field and, therefore, also when a ball is in or out.

To comprehensively answer this article’s main question, it is first important to answer the question: is the line in or out in tennis?

When a tennis ball touches any part of the line, even just a sliver, the ball is considered in. You must be able to see a bit of space between where the ball lands and the line to call the ball out of bounds.

Tennis balls are made of rubber, which allows them to compress when being hit and when contacting the court.

This makes the surface area of the ball larger when it makes an impact.

So, the point of contact is what determines if the ball is in or out.

Making this call can be tricky, especially in the heat of the moment when we so badly want our opponent’s ball to be out.

Be fair, and if you think the ball may have even slightly grazed one of the lines, call it good and keep battling.

Now that we know the ball is in when it hits the line, it is still important to understand the line rules of tennis.

This is because different rules apply to singles than to doubles in tennis.

Let’s begin by establishing that there are two sets of sidelines on a tennis court.

The first set of sidelines is used when playing singles, and the second one is used when playing doubles.

Together with a small section of the baseline and the net, they make what we call the doubles alleys.

Tennis court line names

When is the ball out of bounds in singles play?

If you are playing singles, one player versus one player, then a ball is considered out when it passes the baseline or the singles sidelines.

When is the ball out of bounds in doubles play?

If you are playing doubles, two players versus two players, then a ball is considered out when it passes the baseline or the doubles sidelines.

For serves, you’ll notice that each side of the court has two service boxes.

Depending on where you stand to serve will dictate where you need to place your serve.

There is a line cutting the court almost in half called the service line. Now, if your serve lands beyond that line, your serve is out.

When serving, the doubles alleys don’t come into play.

If the ball lands beyond the singles sideline (the outer edge of the service boxes), the ball is out.

The center service line can be tricky when first playing tennis and remembering all the game’s rules.

The center service line is considered in when the ball lands on it, no matter what side of the court you are serving from.

How to Call a Ball Out in Tennis?

The general rule of calling a ball out is that a player needs to make the call audibly, visually, and quickly.


Say the word out loud enough for your opponent(s) to hear you.


Stick your index finger up – which is the universal sign for a ball being out of bounds – so that your opponent(s) can see it.


Be quick about the call you make; hesitating to make the call will have your opponents call into question the legitimacy of the call.

When returning serve, you must call the serve out as soon as you see it land because, again, waiting will make it look like you are unsure of your call.

If you remember only one thing from reading this, let it be: when in doubt, call it in.

And if you go back on the out call you made, your opponent gets the point. It’s just good sportsmanship.

Etiquettes to call a ball out in tennis:

  • Never call a ball out when it is still in the air. Some shots look like they are obviously going out but always wait until the ball lands to make the call. The wind becomes a factor if you’re playing outside, and the ball may surprise you and land in the court.
  • A clear, firm “out” is all that is needed to call the ball out. There is no need to describe how the ball was out. It goes back to the golden rule and treating others how you would like to be treated.
  • Use a neutral tone when making the call. There’s no reason to be aggressive, sarcastic, or arrogant about calling your opponent’s ball out.
  • Please don’t argue with your opponent’s call unless it’s very obviously a bad call. Ask in a neutral but confident tone, “are you sure?” Then it’s up to them, to be honest, or not.
  • If you are a spectator of a match, fight the urge to make calls or correct calls. Unfortunately, if you’re not on the court playing, you don’t get a say.

Who Decides if a Ball is Out in Tennis?

When playing recreationally, it’s the players who are left to make their own calls.

Sometimes, a judge roams multiple courts in tournaments, but that’s typically a rare occurrence.

When playing singles, be sure to be loud and firm with your calls since there are only two of you on the court.

The same goes for when you are playing doubles.

However, there are some nuances:

  • The receiving net player is the one who should make the call if the serve is out.
  • If there is a disagreement about the call between partners, the ball is considered in, out of good faith.

Professionally, the players don’t need to make their own calls. They have a chair umpire and line judges on the court with them.

Umpire and line judges in tennis:

The umpire sits in a tall chair to the side of the tennis court, parallel with the net.

Their primary duties are to call out the score and make any final rulings on calls.

They also make sure that the rules are being followed.

Umpires on-court duties include:

  • Announcing the score after every point, game, and set.
  • Handling arguments between players.
  • Deciding to delay matches due to weather.
  • Calling warnings or violations on players.
  • Announcing the final score.
  • Overruling line calls made by the line judges.
Umpire calling a ball out

A line judges are the people who stand behind the players at the back of the court.

They’re even sat far back on the sidelines to help with line calls and service calls. They are the ones that call all shots relating to the assigned lines.

Each judge is assigned one line to watch, meaning there are typically nine line judges used in a professional match.

If they are short-staffed, they are given a system of lines to watch.

The line judges will make a loud, verbal call of “out.” They will use the word “fault” for a serve.

Line judges also have hand signals they use in conjunction with different calls:

  • The hand signal for a good ball is two hands together, thumb to thumb, showing the tops of the hands.
  • The signal for an out ball is the extension of the arm shoulder high in the direction the ball was out.
  • When their view is obstructed, they signal this by holding their hands behind their head which means the chair umpire is then the one to make the line call.
Line judges calling a ball out

They are also responsible for calling foot faults, which is when the server’s feet touch the baseline before they contact the ball.

This call will be made verbally and paired with a vertical extension of their arm with an open palm.

Hawk-Eye system in tennis:

Since 2006, tennis has used Hawk-Eye, technology that helps with line calls.

Hawk-Eye is a computer vision system used to visually track the ball’s trajectory and display a profile of its most likely path as a moving image.

The onscreen representation of these results is called Shot Spot.

Hawk Eye calling a ball out

Hawk-Eye is used at most major tennis tournaments like:

  • Wimbledon
  • Australian Open
  • U.S. Open
  • Davis Cup
  • Tennis Masters Cup
  • The Queen’s Club Championships

Hawk-Eye is now widely used at all professional-level events, except clay-court tournaments.

Being the only grand slam played on clay, the French Open doesn’t use the technology because of the marks left on the clay where the ball bounces.

Essentially, the ball leaves evidence on clay courts that make it easy to see when making or disputing a call.

In recent years, a few clay tournaments have adopted Hawk-Eye. It is only used when the bounce of the ball is in doubt.


Play by the tennis rules, stay honest and keep your opponent honest.

Remember to make your line calls verbally and visually so that there is no confusion to be had when you are in the middle of a match.

Most importantly, tennis is a game – so, have fun!

Brian Henderson

I am what you might call a true tennis fanatic. When I am not on the tennis court teaching or playing myself, I am probably writing an informative article about tennis. My goal is to get as many people as possible excited and informed about tennis.
November 18, 2021
Published: November 18, 2021