A weight and balance calculator for the C152LR- long range fuel tanks. (if you have a standard tank C152, use the C152 app, as the fuel tank arm is different)
Enter the weight (in pounds) for each position in the aircraft, and the amount of fuel (in gallons), and the calculator will let you know if you are out of limits on weight or CG. The forward and aft CG limits are calculated using formula derived from the aircraft limit chart.