Every bowler wants to know one number: how fast am I?
For decades that answer needed a radar speed gun: the kind TV broadcasts use, which costs hundreds of dollars, needs someone to stand behind the net pointing it, and gives you a number with no context. Most club and junior cricketers have simply never had their speed measured at all.
That's changed. A modern phone camera, running computer-vision ball tracking, can now measure a delivery's speed from a single recording of your bowling, no radar, no sensors on the ball, no special hardware.
How phone-based speed measurement works
When you record a delivery, the software does four things:
- Detects the ball in every frame. A neural network trained on thousands of deliveries finds the ball frame by frame, even when it's a few pixels wide.
- Calibrates the scene. The pitch itself is the ruler: the Laws of Cricket fix the pitch at 22 yards (20.12 m) between the stumps, so once the software locates the creases and stumps in the frame, it knows how many metres each pixel represents. This is also why a full-pitch view matters: a cropped pitch means a guessed ruler.
- Fits a trajectory. The frame-by-frame ball positions become a physical flight path: release, bounce, and arrival, with drag and gravity accounted for.
- Reads speed off the trajectory. Distance over time, measured at release, the same definition a radar gun uses.
That last point matters: the ball slows noticeably through its flight (air drag takes several km/h out of a delivery by the time it reaches the batter), so where speed is measured changes the number. Release speed is the standard.
How accurate is it?
Honest answer: it depends on your setup, and anyone quoting you a single accuracy figure for phone tracking without stating their test conditions is selling something.
What's worth understanding is where the error comes from. Frame rate sets the floor: at 60 fps each frame is about 17 milliseconds, and the trajectory is fitted across many frames, so more frames means a tighter fit. Calibration sets the scale: if the software can't see the creases clearly, its ruler is wrong and every number scales with it. Lighting, camera shake and a partially framed pitch all degrade the fit.
What this means practically: treat the absolute number with some humility and the trend with confidence. A well-set-up phone will tell you reliably whether your average is climbing across a season, and whether your quickest ball is repeatable, which is what actually informs training. Comparing your phone reading against a broadcast speed gun ball-for-ball is the one thing it is not for.
Setting up your phone correctly
- Film from behind the bowler's end, elevated if possible, behind the net, roughly in line with the stumps. This gives the tracker the full flight path.
- Keep the whole pitch in frame. The calibration needs the creases; if the batting end is cut off, the ruler is gone.
- Use a stable mount. A tripod or a fence mount beats a hand-held phone every time: a shaking camera blurs the ball.
- Good light. Outdoor daylight is ideal. Indoor nets work if the lighting is even; avoid filming into a low sun.
- Record at 60 fps if your phone offers it. More frames = more ball positions = a tighter trajectory fit.
What to do with the number
A speed reading on its own is a party trick. A speed reading per ball, per session, over months is a training tool:
- Track your average and peak across a session, fatigue shows up as a falling average long before you feel it.
- Compare run-up changes, action changes, or a new coach's advice against real numbers instead of feel.
- Combine speed with line, length, and bounce point: a ball-tracking app measures those from the same footage, which a radar gun never could.
The short version
You need: a phone, a tripod, a standard-length pitch, and a ball-tracking app. You don't need: a radar gun, sensors, or anyone standing behind the net. Record from behind the bowler's arm with the whole pitch in frame, and you'll have professional-style speed, line and length numbers for every ball of your net session.
Zoota tracks every delivery you bowl: speed, line, length, bounce and a 3D replay, from a single phone recording. It's free to try on Android.
Sources
- Marylebone Cricket Club. The Laws of Cricket, Law 6: The pitch: 22 yards (20.12 m) between the stumps.