Gas gauge not accurate

My gas gauge needle on the panel will not go to the full mark. It sits at 1/2 after I put gas in it. Typically when I am filling my tank the gas pump kicks off and I am still able to put in anywhere between $10.00 to $20.00 more worth of gas. I am unsure if I ever have a full tank. I do have a digital gas gauge panel in my car as well, I have a feeling that there may be something wrong with that as well because after I put gas in my car it will still say low fuel level then after letting it sit it will say that I have 70 miles to empty (used to be before issues, I could have a full tank and it would say 225 miles to empty). After driving it for about a week, it will go to 50 miles to empty and say low fuel then it will go up to 65 miles to empty. I have run out of gas before while sitting at a light with both of my young boys in the car due to this problem. Even then my gauge on my dash still said 14 tank.