You should be able to look in the owners manual or somewhere and figure out how big the tank actually is too, that will give you a reference for the next fill up when the gauge is telling you its half full. If you have a 20 gallon tank, and you drive it till the gauge tells you its half full and you fill up again, and only put in 4 gallons, something is wrong with gauge or sender, etc. Also record your mileage when you fill up, then you can figure out your mileage, and use your odometer or tripometer as your fuel gauge until you have better weather to fix it in.
Sean