Which is more accurate, the speed shown on a speedometer or a sat nav?

On the occasions I use my smartphone as a sat nav, I get a readout of the speed of the car on the screen. It always shows a slower speed than my speedometer by 3-4mph. Since this can make all the difference in some areas where they have speed cameras set to catch drivers going above 20 mph, would you regard the smartphone figure as a more accurate and reliable guide to avoid being caught out?

Asked on 16 March 2020 by Neil Littman

Answered by Georgia Petrie
The sat nav on your smartphone is more accurate, speedos generally read a little over what you're actually doing.
Tags: speedometer
Similar questions
What is the most accurate speed indicator - analogue speedometer, digital speedometer or GPS on sat navs?
If the smaller of the two numbers on a tyre relates to height will remaining on the same size wheel with taller tyre not affect speedo readings?
When using Google Maps I noticed a 3mph discrepancy between my car speedometer and the phone sat-nav. Which should I rely on?

Value my car

Save £75 on Warranty using code HJ75

with MotorEasy

Get a warranty quote

Save 12% on GAP Insurance

Use HJ21 to save on an ALA policy

See offer