Know your speed.
In one glance.

In open sky with a clear view of the satellites, modern phones report speed within about ±0.5 to 2 mph (roughly ±1 to 3 km/h). The high-accuracy reading uses both position differences and the Doppler shift of the satellite signals, so even slow movements like walking are picked up reliably. Accuracy drops in three common situations: inside buildings, where walls absorb the signal; between tall structures (the "urban canyon" effect), where reflected signals make the position drift; and in tunnels or parking garages, where the signal disappears entirely. When the signal weakens, the status indicator switches from "GPS Ready" to "Acquiring" and waits for a stronger fix. The accuracy radius is shown next to the status pill in meters: anything below 25 meters is treated as ready. For the most accurate reading, step outdoors with a clear view of the sky and wait 10 to 30 seconds for the GPS chip to lock in. After that, the speed shown on the dial is typically within a fraction of a mile per hour of your true speed.

Yes, the speedometer keeps working without internet once the page is loaded. Your device's GPS chip does the actual measuring locally, and the page does not need to talk to any server during use. The site only needs an internet connection for that initial page load, which fetches the HTML, the CSS, and the small JavaScript bundle that draws the dial. After that, you can put your phone in airplane mode (with Location Services left on) and the speedometer will continue to read your speed normally. This makes it useful for road trips through areas with patchy cellular coverage, like national parks, mountain passes, or country highways. If you expect to be offline often or for long stretches, the free iOS companion app is a better fit. It caches everything on first launch, recovers gracefully from background suspension, records full trip history offline, and reopens instantly even after weeks without a connection. The web version is best for quick reads when you have a fresh page open; the app is best when you need a tool you can rely on without network.

Usually one of three things, in order of how often it comes up. First, you have not granted location permission yet. Tap "Begin" and grant the browser permission when prompted. The dial cannot read GPS without this. Second, you are indoors without a GPS fix. Walls, ceilings, and even thick window glass absorb the satellite signal. Step outside, and within 10 to 30 seconds the status pill should switch from "Acquiring" to "GPS Ready" with a green indicator. Third, your device is still acquiring satellites. A "cold start", the first GPS reading after your phone has been off or in a sealed environment for hours, can take up to a minute. Subsequent fixes are much faster because your phone caches almanac data. If you have waited a couple of minutes outside with an open sky and the dial still reads zero, try refreshing the page and granting permission again. On iOS, also check Settings, Privacy, Location Services, Safari Websites and confirm it is set to "While Using" or "Ask Next Time", not "Never".

High-accuracy GPS tracking does use some battery, but less than people often assume. On modern phones with the screen on, expect roughly 5 to 12 percent per hour with this site open. The largest portion of that is actually the screen itself; the GPS chip alone is energy-efficient. To keep things light, we pause GPS tracking automatically when the browser tab is hidden or backgrounded, so checking your speed during a 5-minute stop costs almost nothing. For longer sessions, recording a full cycling ride, a road trip, or a hike, the free iOS companion app is built specifically for background use and is much gentler on the battery. The app uses Apple's motion coprocessor to filter low-quality readings, suspends the screen safely, and resumes recording without losing data when you pull your phone out hours later. If battery is a serious concern, a long backcountry day for example, use the iOS app and lower screen brightness; with both, you can run continuous GPS tracking for 8 hours and still have plenty of charge left.

No. Your GPS coordinates and speed are read by the browser, drawn on the dial, and thrown away after each frame. We never upload, store, or share them, and no account is required to use the site. There is no server-side database of users; there is no cookie that ties your visits together; there is no telemetry channel that quietly forwards location. The site does use Google Analytics 4 to measure basic page-level usage, page views, clicks on the App Store badge, the QR code, and the FAQ section, theme and unit preferences when toggled, and whether geolocation was requested, granted, or denied as a state flag, but no GPS coordinates, no speed value, and no precise device identifier is included in any analytics event. You can verify this yourself in your browser's developer tools under the Network tab: while the speedometer is running, you will see no outbound requests carrying coordinates. The free iOS companion app stores trip records locally on your device for the history feature, and those records are also never uploaded. The full list of cookies and analytics events is documented on our Privacy page.

It is the only way a browser can read GPS speed. The Geolocation API is gated behind explicit, per-site permission by every modern browser, including Safari, Chrome, Firefox, and Edge. This means we cannot silently access your location when you visit the page; you must actively tap "Allow" in the browser's prompt, and you grant permission only to gpsspeedometer.io and not to any other site. That is the right design, and we agree with it. Without this permission gate, any random webpage could track you whenever you visited. You can revoke the permission anytime in your browser settings: in Safari on iPhone, tap "AA" in the URL bar then Website Settings; on Chrome, tap the lock icon then Site Settings; on desktop browsers, click the lock icon next to the address. Permission revocation takes effect immediately. We also do not use any clever workarounds like IP-based geolocation or Bluetooth scanning to estimate your position; if you deny the GPS permission, the speedometer simply does not work, by design.

Most factory car speedometers are calibrated to read slightly high, usually 2 to 5 mph (about 3 to 8 km/h) above your actual speed at highway speeds. This is intentional. Manufacturers have legal margin requirements: in the EU, the speedometer must never read low, and most jurisdictions allow it to read up to 10 percent over plus 4 km/h. An over-reading speedometer keeps them safely inside the rules; an under-reading one creates liability. Your car's dial is also affected by tire wear, tire pressure, and aftermarket wheel sizes, bigger wheels make the speedometer read low, smaller wheels make it read high. A GPS reading is a fair second opinion because it derives speed directly from your position relative to satellites, with no mechanical assumptions. It is one of the most common reasons people use this tool: a 5-minute drive on the highway shows you exactly how much your dashboard is over-reporting. That said, your car's speedometer is the legally relevant one in a roadside dispute. GPS is great for verifying calibration, racing telemetry, or curiosity, but the police officer is looking at radar and your dashboard, not your phone.

The iOS app adds quite a lot. Trip recording captures every drive, ride, or run with distance, duration, top speed, average speed, and route. Trip history lets you scroll through every previous session and replay it on a map. The ghost-pace feature lets you race against your previous best on the same route, with the dial showing both your current speed and the time difference in real time. HUD mode flips the display horizontally so you can rest your phone face-up on the dashboard and read its reflection in the windshield, like a heads-up display in a high-end car. Live maps track your position with the speed overlay during recording. Speed-over-time charts show you exactly when you accelerated, when you held a steady cruise, and when you slowed down. The personal-best tracker keeps your fastest run on each route or distance. The web version is a live read, perfect when you just want to glance at your speed or verify a car's speedometer. The app is a full driving journal, a coach for riding and running, and a permanent record you can scroll through years later. Both are free.

The exact conversion factor between miles per hour and kilometers per hour is 1.609344. So 1 mph equals exactly 1.609344 kph, and conversely 1 kph equals 0.621371 mph. To convert in your head, multiply mph by 1.6 (or divide kph by 1.6). For example, 60 mph is roughly 96 kph, 100 kph is roughly 62 mph, and 130 kph is about 81 mph. For an exact figure on any value, use our free converter tools: MPH to KPH converter or KPH to MPH converter. Both pages include a live calculator, the formula, and a full conversion table. The MPH/KPH toggle on the speedometer itself also switches the live reading instantly between the two units, so you do not have to do the math while moving. Most countries outside the US, UK, and a handful of others use kph as the standard road speed unit; understanding both is useful when reading car specs, watching international racing, or planning travel.