Two unknown variables. How wide is the tire when mounted on your rims? The size printed on tire is as meaningless as the pressure printed on the sidewall. How much do you weigh? Which also includes what you carry on the bike.
30psi sounds close to me. You're riding it, how does it feel? When going that low 1 or 2 psi makes a difference. Seat of your pants got you to a good starting point, if you are concerned about better than that you will want an accurate gauge.