How fast am I going?

This page is a speedometer that works in your web browser. It uses the GPS in your phone to show how fast you are going right now. You do not need to install an app or make an account.

The speed updates each time your phone gets a new GPS position, usually about once each second. You can show your speed in miles per hour, kilometers per hour, knots, meters per second, or mach.

How to check your speed

1. Open this page on a phone or tablet that has GPS.
2. Allow location access when your browser asks.
3. Start to move. Your speed shows at the top of the page.
4. Select a unit below the speed to change the display.
5. Keep the page open and the screen on to see live updates.

If you are in a car, give the phone to a passenger or put it in a mount. Do not look at your phone while you drive.

Why does my speed not show?

The speed shows only when your phone is moving and has a good GPS signal. When you stand still, the speed shows zero. On some phones, the display stays empty until you move.

Other causes:

• Location access is off. Allow location access for your browser in your phone settings, then reload the page.
• The signal is weak. Tunnels, parking garages, dense forest, and tall buildings block GPS signals. Move to a location with a clear view of the sky.
• The device has no GPS. Most laptops and desktop computers find their location from Wi-Fi networks. This gives an approximate position but no speed.
• The screen turned off. Most browsers stop location updates when the screen locks or when you change to a different app.

How does a GPS speedometer work?

Your phone receives radio signals from a group of navigation satellites. These include GPS and, on most new phones, other systems such as Galileo and GLONASS. The phone uses the signals to calculate its position on Earth.

The phone does not only compare two positions to find your speed. It also measures the small change in the frequency of each satellite signal as you move. This change is the Doppler effect. Speed from the Doppler effect is more stable than speed from position changes alone.

Your browser gives this speed to the page through the Geolocation API, together with your heading. The heading is your direction of travel, in degrees clockwise from true north. The page also shows this as a compass direction, such as northeast.

How accurate is it?

With a clear view of the sky and a steady speed, a phone speedometer is usually accurate to within about 1 mph (1 to 2 km/h). Accuracy is lower when the signal is weak, when you accelerate or slow down quickly, and in the first seconds after you open the page.

A GPS speed is your true speed over the ground. Your car speedometer can show a different value, for these reasons:

• Most cars show a speed that is a little high. In Europe and many other regions, the law (UN Regulation No. 39) does not let a speedometer show less than the true speed. Manufacturers usually set them to show a few percent more.
• Tires change the reading. A car speedometer counts wheel rotations. Worn tires, low pressure, or a different tire size change the distance for each rotation.
• GPS updates are not instant. If you change speed, the GPS value can be one or two seconds behind your car.

On a steady road, the GPS speed is usually the better value. Use your car speedometer to obey speed limits, because it updates instantly and does not need a signal.

Units of speed

To convert, 1 mph is 1.609 km/h, and 1 km/h is 0.621 mph. 1 knot is 1.151 mph.

Ways to use this speedometer

• Driving: Check a car speedometer that you think is wrong, or check your speed in a rental car with unfamiliar gauges.
• Cycling: See your speed on a bike that has no bike computer.
• Running and walking: Find your pace. At walking speeds, the value can change more because the GPS error is large compared to your speed.
• Trains and buses: See how fast you travel when there is no speed display.
• Boats: Show your speed in knots.
• Airplanes: Many phones can get a GPS signal near a window. Airplane mode turns off the mobile network, but on many phones GPS continues to operate. Speed in an airplane is your ground speed, not your airspeed.

More information on this page

Below your speed, the page also shows your heading, compass direction, elevation, and GPS coordinates. Some devices also report your floor level in a building. To learn more about the height of your location, go to What is my elevation?