Fuel gauge does not go beyond half tank on 2007 xl7

Is it taking the proper amount of gallons for the tank size. 18.6 gallon tank capacity when completely physically empty. May be the Fuel sending unit. It has a float attached the measures fuel level. It's a little sensor arear the float end rub across and they do go bad. If tank is taking proper fuel capacity then this would be next. Depending on performance I may ignore it and keep track of mileage for fuel consumption. Not a fun repair dropping the fuel tank and all. Just be careful not to end up stranded. Other uncommon culprits on circuit issues like a fault somewhere causing voltage issue, bad cluster, etc. Good luck!