Pilot reported possible problem with fuel calculations after running out of fuel in flight and landing at a nearby airport.

Narrative

I ran my aircraft out of fuel. I had thought I had enough fuel onboard to more than cover my minimum fuel requirements to complete the flight. The engine sputtered; fuel pressure dropped; the prop stopped. I turned towards the closest airport and trimmed for best glide speed. I [announced] on 121.5; realized that I needed to be speaking on the field's CTAF and switched to that. Other pilots were relaying to an ATC facility. I was able to make the field and make an otherwise uneventful landing on Runway XX. The airport Manager met me with fuel; the engine started without further issue. The airport Manager had spoken with someone at an ATC facility and he relayed to them I was fine; the plane was fine. There was no number given to him for me to call. I filled the plane with fuel and took a long walk before continuing my flights. This is a relatively new aircraft with three different fuel gauges and it has a very low burn rate. I have come to not trust two of the gauges. The fuel calculator is what I was relying on. My own inputs into fuel calculator have been the problem. The tank is labeled as 20 gallons; but you can put more into the tank than that; or less to keep it lighter. You can fill the tank and add this value to the calculator; or you can reset the calculator and put in the value you 'know' to be in there. I reset the calculator today; but often I have just added to the calculator what I just pumped. Before today; the last time I reset the calculator was likely fifty hours of flying ago- maybe as many as 15-20 different fuel fill situations. I think I should go from a reset calculator more often; or every time I fill up.