Racing GPS Speedometer

Choose your units and activity

Select km/h, mph, knots or m/s. Walking gives the dial a 30 km/h equivalent range; cycling uses 80 km/h. Passenger mode keeps the wider theme range. These change the display, not your measured speed.

Start GPS and check the signal

Press Start GPS and allow location access. The first position may not include speed. Wait for a fresh reading, and use Settings to inspect its source, position accuracy and age instead of assuming the device has stopped.

Pause, review and keep your summary

Pause when you finish. Review trip scrolls to the statistics below the dashboard. Download PNG for a branded snapshot or CSV for a spreadsheet. Reset asks before clearing an existing trip.

A walk, not a race

Use the walking range to see small changes more easily, then compare pace in minutes per kilometre or mile. Slow movement can be hard to separate from position drift, so treat a stop-start walking estimate as approximate rather than a fitness tracker record.

A cycling session

Set your phone securely before you leave. The cycling range keeps ordinary riding speeds visible without using the whole vehicle-scale dial. Review maximum speed, moving average and active time afterwards; do not handle the screen while riding.

A train or bus journey

As a passenger, compare the changing speed with the stops along your route. A tunnel can interrupt reception without interrupting the journey. We stop connecting measurements across long gaps so that a later position does not suddenly create a false distance jump.

Learning about motion

Try the demo to explore the needle, themes and unit conversions without sharing a location. A classroom can compare 10 m/s with 36 km/h, then discuss why a precise-looking number is not the same as a precise measurement.

Four units, one measurement

The engine keeps speed in metres per second. The display converts it using 3.6 for km/h, 2.2369362920544 for mph and 1.9438444924406 for knots. A change of units also changes the trip-distance label: miles for mph, nautical miles for knots, and metres or kilometres otherwise.

Ranges for different activities

Walking and cycling make the dial easier to read at everyday speeds. Passenger mode restores the classic, digital or railway 240 km/h range, the racetrack 500 km/h range or the airplane 1,500 km/h range. If speed exceeds a dial’s range, the number remains visible even though the needle reaches its limit. Coloured dial zones are decoration, not speed-limit advice.

Five appearances without losing your trip

Classic uses a needle; Digital favours a large numeric display; Railway, Racetrack and Airplane add their own scenes. Switching appearance within the tool keeps the same session. The related pages below let you open a particular dashboard directly.

Demo and live data stay separate

Try demo pauses GPS tracking and runs a simulated acceleration. It does not increase the real distance, maximum or moving average. The screen and PNG label the simulation, while the CSV remains a real-session summary. Stop the demo or press Resume GPS to return to measurement.

Elapsed, active and moving time

Elapsed time runs from the first accepted position, including pauses. Active time excludes a manual pause or stopped tracking. Moving time includes accepted movement intervals above 0.45 m/s. Moving average divides distance from those intervals by their duration; it is not an average over your entire outing.

Freshness and useful diagnostics

A speed becomes unavailable after ten seconds without a fresh position. Settings show the age of the last update, the browser’s permission state and whether speed came from the device or from consecutive positions. Position accuracy is a radius in metres, not a guarantee that the displayed speed is accurate to a particular amount.

Fullscreen, wake lock and HUD

Fullscreen gives the display more room; Escape exits on browsers that support it. Keep screen awake requests a screen wake lock while tracking, but support and battery policies vary. Mirror display flips the dashboard for a reflected HUD experiment; it is not an approved substitute for vehicle instruments.

A summary you can keep

The PNG combines the displayed speed, its live/demo/paused status, real trip statistics, time of export and ClockTools branding. CSV gives you labelled summary fields for a spreadsheet. Neither export includes a route trace or raw latitude and longitude. Your trip is held in this page’s memory, so save the summary before closing or reloading it.

Power is only one part of the challenge

A faster car has to manage more than engine output. Aerodynamic resistance, stability, tyres, gearing, cooling and the surface all shape what is possible. A car designed for a circuit lap can make different compromises from one designed for a straight-line top-speed run.

That is why we link specific models rather than treating every exotic badge as a 400 km/h claim. The official examples below include a recorded run, stated specifications and a design focused on reducing drag. They are not interchangeable achievements.

Records, specifications and predictions need different labels

A published record describes a particular vehicle and run. A manufacturer’s listed maximum is a specification, and a design ambition is not yet a measured top-speed result. Comparing them responsibly means keeping those distinctions visible.

The Chiron record vehicle is therefore identified as the Super Sport 300+, not simply any Chiron. Likewise, the Tourbillon’s Speed Key condition matters. We do not turn an optimistic simulation or a different model’s achievement into a verified claim for another car.

What a passenger can learn from our racing display

The wider dial makes a high-speed reading easier to place within its range. It does not improve the underlying measurement, certify acceleration times or replace dedicated lap-timing telemetry. Large gaps between fixes matter more as distance travelled per second increases.

Only use the tool as a passenger where conditions and rules allow. High-speed testing belongs to controlled venues with qualified teams and appropriate equipment. We have not tested ClockTools at these cars’ top speeds, and the demo is only an interface simulation.

The story began with a radio signal

Long before a phone could show a moving blue dot, researchers noticed that a satellite’s radio frequency changed as it moved towards or away from an observer. Observations of Sputnik in 1957 helped demonstrate how that Doppler shift could reveal an orbit. Reversing the problem suggested another possibility: if a satellite’s path was known, its signal could help locate the receiver. GPS grew out of a much longer history of radio navigation, engineering and timekeeping, rather than a single smartphone invention.

That history is useful when you look at our dial. The screen is the final, friendly layer of a measurement chain involving satellites, receivers, operating-system services and a browser. A beautifully animated needle cannot repair a weak signal at the start of that chain.

Why a location system needs exceptionally good clocks

GPS satellites broadcast timed signals. A receiver compares when a signal was sent with when it arrived to estimate the distance to each satellite. In the basic three-dimensional solution, at least four satellites are needed to solve for position and the receiver’s clock offset. Satellite clocks are therefore part of the measuring instrument, not merely a way to display the time of day.

The same infrastructure supports time transfer as well as navigation. NIST explains how GNSS signals help compare clocks across distant locations. ClockTools began with time tools, so this connection is especially fitting: the speed on this page depends on a world of coordinated timing even when all you see is a number in km/h.

Ground speed and the dashboard do not always agree

A vehicle speedometer usually infers motion from wheel or drivetrain rotation. Tyre size, pressure, calibration and the design of the instrument can affect that reading. A location-based estimate follows a different route: the device may report horizontal speed directly, or we may estimate it from the distance between accepted positions. Neither method makes our browser tool a calibrated reference instrument.

In an aircraft, the distinction becomes more important. Ground speed describes motion relative to the Earth; airspeed describes motion relative to the surrounding air. Wind can change the relationship between them. Our airplane theme does not measure airspeed, and a visually impressive aircraft dashboard should never be mistaken for a flight instrument.

Read the journey, not just the biggest number

Imagine two cyclists covering 12 kilometres. One rides steadily for 40 minutes; the other stops for a ten-minute conversation. Their moving averages may be similar, but elapsed time tells a different story. That is why we keep elapsed, active and moving time separate instead of hiding all three behind one average.

A practical pace example is 1.5 m/s: that is 5.4 km/h, or approximately 11 minutes 7 seconds per kilometre. But if your location uncertainty spans tens of metres, a short walk may not provide enough displacement for a reliable estimate. Watching the source, freshness and position accuracy is often more informative than collecting extra decimal places. Our summary helps you interpret what was measured, including the limits.