A double fault gives away the point without your opponent hitting a ball. Under the Rules of Tennis, two consecutive faults lose the point, so your second serve has one main job: start the rally. Most players try to do that by slowing down, and that usually makes the problem worse.
The fix is more spin at full arm speed, a toss you can repeat, and practice that includes pressure. This guide shows how to find out whether your problem is technique or pressure, and then how to fix either one.
How common are double faults?
SwingVision has published data from more than 250,000 sessions by its app users. It does not say how it assigned NTRP levels, so treat these SwingVision figures as a rough guide.
| NTRP level (SwingVision data) | Double faults per match | First serves in |
|---|---|---|
| 2.5 | 2.51 | 55.1% |
| 3.0 | 3.49 | 53.3% |
| 3.5 | 3.71 | 53.5% |
| 4.0 | 3.58 | 54.4% |
| 4.5 | 3.23 | 55.8% |
| 5.0 | 3.21 | 55.5% |
In SwingVision's numbers, about 45% of first serves miss at every level, so you hit a lot of second serves. Its double-fault counts stay above three per match from 3.0 to 5.0, so they do not simply disappear as you improve.
Why double faults happen: technique or pressure?
Run this test before you change anything. Hit 10 second serves in a calm practice, five to each box. Then hit 10 more with these rules: one ball at a time, a walk to the back fence between serves, and the score 30-40 said out loud before each one. Count how many land in. The target of 7 of 10 is a practice benchmark we suggest, not a research figure.
| Calm serves | Pressure serves | What it means | Start with |
|---|---|---|---|
| Under 7 of 10 | Any result | A technique problem | Spin, grip and toss, below |
| 7 of 10 or more | Under 7 of 10 | A pressure problem | The pressure routine, below |
| 7 of 10 or more | 7 of 10 or more | Your serve works in practice, so look at match habits | Reviewing a match video, counting your double faults by hand |
Where the miss goes tells you more. Note it for a week, then confirm the cause on video.
| Where it goes | Likely cause | Video check |
|---|---|---|
| Net | Your arm slows down, or the toss drifts forward and you hit down | Compare your arm speed with your first serve. Check that the racket is rising at contact. |
| Long | Too little spin to bring the ball down, or a toss drifting behind you | Pause at contact. If the strings face the target squarely, you are hitting through the ball, not brushing up it. |
| Wide | Your body opens early, or the toss drifts to the side | From behind, check where the toss goes and whether your shoulders stay sideways until the swing goes up. |
Add spin instead of slowing your arm
The net is 0.914 m (3 feet) high at the center and 1.07 m (3.5 feet) at the posts, and the service line is 6.40 m (21 feet) from the net. A flat serve has a narrow window: it must clear the net and still come down in time. Spin pulls the ball down, so you can aim higher over the net and still land in the box.
When you slow your arm, you lose spin as well as speed. The ball flies lower, and you have less margin for the same target. Keep the swing fast and change its direction: more up and across the ball, less through it. The ball will still travel more slowly, because more of your swing goes into spin.
Try this spin ladder. If you miss a target, go back one step. Do not slow your arm to make the numbers.
- Stand on the service line and hit 10 serves that rise over the net and drop into the box. Swing fast. Target: 7 of 10.
- Move halfway back to the baseline and repeat. Target: 7 of 10.
- From the baseline, hit 10 to each box, clearing the net by about a racket length. Target: 7 of 10 in each box.
Slice or kick: which second serve should you use?
Both add spin, each in its own direction. The directions below are for a right-hander, and left-handers should reverse them.
| Feature | Slice serve | Kick serve |
|---|---|---|
| Swing direction | Across the ball, brushing its right side | Up the back of the ball, from about 7 to 1 on a clock face |
| Toss | A little to the right of your head and slightly in front | Closer to overhead, a little further left and less in front |
| Ball flight | Curves to your left and stays lower | Clears the net higher, dips, then bounces up and to your right |
| What it asks of you | Easier to learn, works with moderate racket speed | More racket speed and a strong upward push from the legs |
| Use it when | You need a safe serve now | Your slice is reliable and you want a higher bounce |
Coaches differ on which to teach first. A practical rule: start with the slice, which many players find easier to land, and add the kick once the slice reaches 7 of 10 from the baseline. If either serve hurts your back or shoulder, stop and see a medical professional.
Grip and toss
Use a continental grip for both serves. Some coaches move the hand slightly toward an eastern backhand grip for more spin, so try that only after the continental grip feels natural. The guide to improving your serve shows how to check your grip and toss on video.
Keep your toss within a small area and repeat it. Under the Rules of Tennis from the ITF (now World Tennis), tossing the ball and catching it is not a fault, so you never have to hit a bad toss. Catch it and start again, but keep in mind that the rules ask you to serve again without delay after a fault.
A pressure routine with a target of 7 of 10
Build the motion with repetition first, then add match conditions. In one study of 83 undergraduates in tennis classes, low-skilled students did better with blocked practice, meaning the same task repeated, while high-skilled students showed no difference. A 2007 review still argued that repetitive hitting alone is unlikely to give the best learning. Move to the next step when you pass the target in two separate sessions.
- Set your routine. Choose the same steps for every serve: the same number of ball bounces, one target, one breath out, then the toss. Use it on every ball below.
- One ball at a time. Hit 10 serves to each box. Walk to the back fence between serves and say a score out loud, such as 30-40 or deuce. Target: 7 of 10 in each box.
- Go deeper. Hit 10 to each box and count only serves in the back half of the box, the part closest to the service line. Target: 5 of 10, then 7 of 10.
- Serve when tired. Before each serve, run to the net and back. Hit 10 serves. Target: 7 of 10.
- Play it. With a partner, play games to 11 with one serve per point, so every miss loses the point. Write down how many serves you land.
Keep the numbers in your phone or a notebook. A count you can compare from week to week tells you more than how the serve felt.
Check your second serve on video
Film five first serves and five second serves from the same side-on position, then watch them in slow motion. Look at three things: does your arm slow down, does the toss move, and does your rhythm speed up? A slower arm is the most useful thing to catch, because it is hard to feel while you are serving.
Upload the two sets as separate clips if you want another view. TennisAI's serve analysis gives a serve score and feedback for each clip. Its listing does not advertise separate first and second serve scores or double-fault counts, so keep that tally yourself. The score is an automated estimate that can be wrong, and it varies with camera angle and lighting, so compare clips filmed from the same spot.
Frequently asked questions
How do I stop double faulting under pressure?
Use the same routine before every serve, and practice one ball at a time with a score said out loud. If you land under 7 of 10 in calm practice, fix your spin and toss first.
Should a second serve be slower than a first serve?
The ball usually travels more slowly, but your arm should not. Keep your arm speed and direct more of the swing up and across the ball, so it gains spin.
What happens if my second serve touches the net and lands in?
It is a let. That serve is replayed, and under the Rules of Tennis a let does not cancel the previous fault, so you are still on your second serve. Some events use an approved alternative to this rule.
How many double faults per match is normal?
SwingVision's own data for its app users shows about 2.5 to 3.7 double faults per match across NTRP levels 2.5 to 5.0. It is vendor data, so treat it as a rough guide.
Should I learn a slice or kick second serve first?
Many players find the slice easier to land, so it is a sensible start. Add a kick when your slice is reliable. Coaches differ on this, so follow your coach if you have one.
See this in your own game
Upload a practice or match video to TennisAI and get feedback on your forehand, backhand and serve.
Sources
- ITF (now World Tennis): Rules of Tennis 2026
- SwingVision blog: The real data behind every NTRP level (vendor data)
- Hebert et al., Research Quarterly for Exercise and Sport: Practice schedule effects on low- and high-skilled students
- Reid, Crespo, Lay and Berry, Journal of Science and Medicine in Sport: Skill acquisition in tennis
This article is general information about tennis training and does not replace a coach or medical advice. Stop and see a professional if something hurts. TennisAI is made by Pace, the publisher of this blog.
