The best app to measure speed depends on what is moving. For your car, bike or run, a GPS speedometer or the speedometer built into Google Maps or Waze works well. For a thrown or kicked ball, however, you need a video-based radar-style app, because GPS cannot track a ball.
Almost every phone can now show your speed. Still, the reading only means something when you match the tool to the job. A phone in a car measures its own movement, so it is good at telling you how fast you are going. By contrast, it cannot point at a passing car or a pitched baseball and read its speed the way a radar gun does.
This guide sorts speed apps into a few clear types instead of ranking app listings, because app names, prices and features change often. So you will learn what each type measures, where its numbers come from, and how far you can trust them.
In short: GPS apps measure you, video apps measure things you film, and neither replaces a calibrated radar or your car’s speedometer when the exact number matters.
Even the app makers say so. For example, Google states that the speedometer in Google Maps is for informational use only, and it tells drivers to confirm their actual speed on the vehicle’s own speedometer.
Convert Any Speed Reading Into Other Units
Speed apps switch between mph, km/h and knots, and ball apps often show feet per second. Enter any reading below to see it in every unit. The converter uses the exact definitions 1 mile = 1.609344 km and 1 knot = 1.852 km/h.
Recommended Tools for Measuring Speed With a Phone
An app is free, but the right hardware makes it far more reliable. First, a sturdy dashboard mount keeps the phone visible and hands-free. Next, a tripod holds the camera still for video-based ball apps. Finally, if you need trustworthy pitch or serve speeds, a dedicated sports radar that pairs with a phone app does better than video alone.
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Key Takeaways
- A GPS speed app measures how fast the phone itself is moving.
- Google Maps and Waze both include a free speedometer you can switch on in settings.
- Ball and pitch apps work from video: they time the ball over a known distance.
- Higher frame rates make video apps far more precise; 240 fps beats 30 fps by a wide margin.
- Phone GPS struggles in tunnels, cities, dense trees and during hard acceleration.
- Google calls its Maps speedometer informational only; your car’s speedometer still counts.
- Never handle the phone while driving; set it up before you move.
Types of App to Measure Speed Compared
Most speed apps fall into one of four groups. Each one gets its number in a different way, so each fails in a different way too.
| App type | What it measures | How it works | Main weakness |
|---|---|---|---|
| Navigation app speedometer (Google Maps, Waze) | Your driving speed | Phone location services (GPS plus other signals) | Lags or drops out with poor sky view |
| Dedicated GPS speedometer app | Your speed, often with trip distance, average and top speed | Phone GPS readings over time | Same GPS limits; top speed can spike |
| Video-based “radar” app | A ball, runner or object you film | Counts video frames over a distance you enter | Depends on frame rate and your distance input |
| Companion app for a radar device | A ball or object in front of the radar | Doppler radar hardware sends readings to the phone | Needs the extra device |
As a result, the first question is never “which app is best?” but “what am I measuring?” If it is you, pick a GPS-based app. If it is something else, pick video or a radar device.
Google Maps or Waze: A Free App to Measure Speed
Before you download anything, check the navigation app you already use. Both Google Maps and Waze can show your current speed on screen, and both can warn you when you pass the posted limit where limit data exists.
Google Maps (Android): tap your profile picture, then Settings, then Navigation, and turn on Speedometer under driving options. Google’s help page also notes that the speedometer changes color when you exceed the speed limit, where that data is available. Our guide to speed limits in Google Maps covers the limit display in more detail.
Waze: open the menu, go to Settings, then Speedometer, and turn on Show speedometer. According to Waze’s help page, you can also choose when the speed limit appears, set what counts as speeding, and turn on a sound alert. Meanwhile, the speedometer turns red when you go over the limit, and the setting carries over to Android Auto and CarPlay.
Dedicated GPS Speedometer Apps
Standalone GPS speedometer apps go further than navigation apps. Typically, they show a large digital or dial readout and add trip tools such as distance, trip time, average speed and maximum speed. Some also offer a heads-up display (HUD) mode that mirrors the numbers so they reflect off the windshield at night.
Because features vary by app and change with updates, read the current store listing before you install one. In particular, look for these points:
- Unit choice: mph, km/h and knots for boating.
- Offline use: speed itself comes from GPS, so it should not need mobile data.
- Clear permissions: it needs location access; it rarely needs your contacts.
- Battery options: a dark screen mode helps on long trips.
For cyclists and runners, fitness apps and GPS bike computers do the same job and also log the ride. If you use an iPhone, see how to measure speed with an iPhone for the built-in options.
Radar-Style App to Measure Speed of a Ball
A phone has no radar, so a “radar gun” app for baseball, softball, tennis or soccer cannot read speed the way a real radar does. Instead, these apps use the camera. First, you film the throw. Next, you mark the frame where the ball leaves the hand and the frame where it arrives. Finally, the app divides the distance you entered by the time between those frames.
That makes frame rate the single biggest factor. For example, a 90 mph pitch covers about 55 feet from release to the plate in roughly 0.417 seconds. Being off by just one frame changes the result as shown below.
| Video frame rate | Time per frame | Result if one frame early or late (true speed 90 mph) |
|---|---|---|
| 30 fps | 33.3 ms | about 83 to 98 mph |
| 60 fps | 16.7 ms | about 87 to 94 mph |
| 120 fps | 8.3 ms | about 88 to 92 mph |
| 240 fps | 4.2 ms | about 89 to 91 mph |
The distance matters just as much. If you enter 55 feet but the real distance is 54 feet, a true 90 mph reading drops to about 88 mph. So measure the distance with a tape, and film from the side, square to the ball’s path.
How to Check an App to Measure Speed for Accuracy
You do not need special gear to test a GPS speed app. Instead, use a known distance and a stopwatch, ideally with a passenger doing the timing.
- Pick a straight, open road. Choose a highway with mile markers and a clear view of the sky.
- Hold a steady speed. Use cruise control so the speed does not drift during the test.
- Time one mile. Your passenger starts the stopwatch at one marker and stops it at the next.
- Calculate the true speed. Divide 3,600 by the seconds taken; for example, 60 seconds means 60 mph and 58 seconds means about 62 mph.
- Compare all three readings. Note the app, the dashboard and your calculated speed at the same moment.
- Repeat in both directions. Averaging two runs cancels out small timing errors and slopes.
In metric areas, use 1 km markers instead: 3,600 divided by the seconds gives km/h, so 40 seconds means 90 km/h.
Accuracy Limits of Phone GPS
Phone GPS speed is usually close on an open road at a steady pace. However, the official US GPS website explains that the accuracy users get depends on atmospheric effects, sky blockage and receiver quality. A phone has a tiny antenna, so it feels all three.
| Situation | What happens to the reading |
|---|---|
| Tunnels and parking garages | Signal is lost; the speed freezes, drops to zero or jumps when it returns |
| City streets with tall buildings | Reflected signals cause jitter and false spikes |
| Dense tree cover | Weaker signal and slower updates |
| Hard acceleration or braking | The display lags by a moment behind the real change |
| Walking or very low speeds | Small position errors become large relative errors |
| Phone deep in a bag or glovebox | Poor sky view and noisier readings |
Your car’s speedometer has its own error, in contrast. It counts wheel rotation, so worn or changed tires shift it, and many cars read slightly high. Our explainer on how speedometers measure speed covers why the two rarely match exactly.
Do and Don’t When Using a Speed App
Do
- Match the app type to what you are measuring.
- Give the phone a clear view of the sky.
- Film ball throws side-on with a tripod.
- Measure the throw distance with a tape.
- Use the highest frame rate your phone offers.
Don’t
- Point a GPS app at another car or a ball.
- Trust a single top-speed spike.
- Rely on an app to argue a speeding ticket.
- Guess the distance in a video app.
- Handle the phone while driving.
Honest Limits of Every App to Measure Speed
Apps are convenient, not certified. For one thing, the speed you see is an estimate that the phone smooths and updates about once a second, so very short bursts can be missed. Moreover, two phones side by side can disagree, because their GPS chips and software differ. In addition, video apps rely on you picking the right frames, and a slip of one frame at a low frame rate can move the result by several mph. Therefore, treat app readings as good guides for training, curiosity and trip logs, not as legal or lab-grade measurements.
When to Use a Dedicated Device Instead
Some jobs need more than a phone. For instance, coaches tracking pitch velocity over a season get more consistent numbers from a sports radar. Similarly, shooters and archers use radar chronographs, and science classes can use light gates; see how to use light gates to measure speed. If you suspect your car’s speedometer is off, a tire or dealer shop can check its calibration.
Frequently Asked Questions
What is the best app to measure speed while driving?
For most drivers, the free speedometer in Google Maps or Waze is enough. A dedicated GPS speedometer app adds trip distance, average speed and top speed.
Can I measure speed with my phone?
Yes. A GPS app measures how fast the phone is moving, and a video app can estimate the speed of a ball you film over a known distance.
Is there an app to measure speed of a baseball?
Yes, video-based apps time the ball between frames over the distance you enter. For consistent readings, use a high frame rate or a radar device with a companion app.
How do I turn on the speedometer in Google Maps?
On Android, tap your profile picture, then Settings, then Navigation, and turn on Speedometer under driving options.
Does Waze show your speed?
Yes. In Waze, open Settings, then Speedometer, and turn on Show speedometer. You can also set speed limit alerts.
How accurate is an app to measure speed with GPS?
On an open road at a steady speed, a GPS app is usually close to your true speed. It gets less reliable in tunnels, cities, under trees and during hard acceleration.
Why does my speed app show a different speed than my car?
Your car counts wheel rotation and many cars read slightly high, while the app uses GPS. Tire size and signal quality also shift the two readings.
Can a phone app work like a radar gun on other cars?
No. A phone has no radar, so a GPS app only measures its own movement. Video apps need a known distance and are not made for traffic enforcement.
Does a GPS speed app need mobile data?
Speed comes from GPS satellites, so many speedometer apps work without data. Maps, speed limits and traffic, however, usually need a connection.
Which app to measure speed works best for running or cycling?
A fitness app or GPS bike computer works best, because it records pace, distance and average speed for the whole workout.
Speed Apps: The Bottom Line
To sum up, pick a GPS speedometer, or simply switch on the one in Google Maps or Waze, when you want to know how fast you are moving. For a ball, use a video app filmed at a high frame rate over a measured distance, or step up to a sports radar.
Above all, remember what the numbers are: useful estimates, not certified readings. Then use the converter at the top of this page to switch any reading between mph, km/h, knots and feet per second.