5 Ways to Know Your Speed Without a Speedometer
- Phone GPS speedometer (most accurate). Open How fast am I going? in your browser. GPS measures true ground speed, usually within 1–2 km/h in open sky.
- Navigation app. Google Maps and Waze can show a speedometer during driving directions — see how to turn it on.
- Distance markers and a stopwatch. Time yourself between kilometer or mile markers on a highway and use the table below.
- Engine RPM and gear. If you know your car’s speed per 1,000 rpm in a given gear (from the owner’s manual or a forum), multiply by the tachometer reading. This is only an estimate.
- Match a known speed. Drive alongside traffic on a road with a known limit or a radar speed sign. Least precise, but works in a pinch.
The Stopwatch Method: Time Between Markers
| Seconds per km or mile | Speed (km/h or mph) |
|---|---|
| 30 s | 120 |
| 36 s | 100 |
| 40 s | 90 |
| 45 s | 80 |
| 51 s | about 70 |
| 60 s | 60 |
| 72 s | 50 |
Let a passenger do the timing, and hold a steady speed for the whole interval. For any other distance, use the speed converter or the formula speed = distance ÷ time.
If Your Car’s Speedometer Stops Working
If the ABS or traction-control warning light came on at the same time, a wheel-speed sensor is a likely cause, because many cars take the speed signal from those sensors. A mechanic can read the stored fault codes with a diagnostic scanner.
Mount the phone in a holder before you drive, and never handle it while moving. The car speed test page has tips for using GPS in the car.
On Foot, on a Bike or on a Train
- Walking or running: the running speed tool shows speed and pace.
- Cycling: the bike speedometer replaces a bike computer — no magnets or wheel-size setup.
- As a passenger: the train speed and flight speed tools work from your seat.
Frequently Asked Questions
How can I tell how fast I’m going without a speedometer?
Use your phone’s GPS with a browser speedometer, or time yourself over a known distance and divide distance by time.
Is GPS speed more accurate than a car speedometer?
At a steady speed in open sky, usually yes. Car speedometers are designed to read slightly high, while GPS measures true ground speed.
Is it legal to drive with a broken speedometer?
Rules vary by country and state, but a working speedometer is generally required for roadworthiness inspections. Get it fixed promptly and drive cautiously in the meantime.