These days tire gauges take many different forms. Old-school car tire gauges are shaped like a pencil and have a metering shaft that pops out from the bottom, indicating air pressure. A pencil gauge can be a bit hard to read, as the numbers on the shaft are small and they aren't super-accurate but they are virtually indestructible and highly portable.

Dial gauges are usually small, featuring a face that is about two inches in diameter. Often the dial is backlit so you can easily read it at night. They may or may not feature a length of hose. Dial gauges are more accurate than pencil gauges, but they may not be happy being bounced around in a glove box.Digital gauges are the most accurate and very easy to read. Most will display air pressure in psi, kPa (kilopascal) or bar (barometric or 100 kPa). Once the tire gauge is pressed on to the valve stem, the gauge can read the pressure in two or three seconds. Digital gauges rely on batteries, so you'll have to keep an eye on power levels.