Guides
Speedometer Guides
Everything you wanted to know about measuring speed — how speedometers work, how accurate they are, and how to get the most out of the one in your pocket.
What Is a Speedometer? How It Works and Why It Matters
A speedometer shows how fast you're moving. Learn how mechanical, electronic, and GPS speedometers work, how they differ from odometers and tachometers, and why accuracy matters.
Read guide 6 min readHow Does a GPS Speedometer Work?
GPS speedometers measure speed from satellite signals, not your wheels. Here's how the Doppler effect makes your phone a surprisingly accurate speedometer — and when it isn't.
Read guide 5 min readGPS vs Car Speedometer: Why Your Car Reads Faster Than You're Going
Most car speedometers show a higher speed than you're actually traveling. Learn why, how big the difference usually is, and which one to trust.
Read guide 5 min readWhy Use a Speedometer App? 8 Practical Reasons
Your car already has a speedometer, so why use an app? From checking accuracy to cycling, boating, HUD displays, and trip logs, here's what a speedometer app is good for.
Read guide 4 min readHow to Check Your Speed on iPhone (4 Easy Ways)
Want to see how fast you're going on your iPhone? Here are four ways, from a free browser speedometer to a dedicated app with HUD and trip history.
Read guide 5 min readHUD Speedometer: Project Your Speed onto the Windshield with Your Phone
A head-up display (HUD) shows your speed in your line of sight. Learn how to turn your phone into a windshield HUD, how to set it up, and when it works best.
Read guide 5 min readHow to Measure Your Car's 0–60 Time with Your Phone
You don't need a race track or expensive equipment to time 0–60 mph. Here's how to measure acceleration safely and accurately with GPS — and what affects the result.
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