There are multiple factors that go into an individual tire’s PSI. A tire’s PSI goes by the weight of the vehicle. Inside the driver’s side door panel, there is usually a placard with the weight and recommended PSI for daily driving.
If there’s no sticker on the door, you can usually find the specs in the owner’s manual. Most passenger cars will recommend 32 to 35 psi in the tires when they’re cold. The reason you check them cold is that as tires roll along the road, friction between them and the road generates heat, increasing tire pressure. Light trucks and commercial vehicles will be different.
If you are off roading, generally, for most off road vehicles 15-20 PSI is a good starting point compared to 35 PSI +/- found on most stock tires. For very soft sand – such as dune running – 10 PSI may be optimal but at tire pressures that low, you are risking the tire coming off the bead.