The minimum bladder tanks size should be about 5 times the GPM rating of your pump. Bigger is better. Since the on/off volume of water in a properly set up tank is about 30% of the tank size, that will give you about 1.5 minutes of cycle.
You may not be able to find the GPM rating of your pump. Check your pump cycle time as described below, after setting the air pressure, to see if you want to replace with a bigger tank.
The tank size I am talking about is the real volume; not those silly labels like calling a 119 gallon tank a WX-350.
You can check your tank as follows:
1. Turn off the power to the pump.
2. Open a cold water valve until you have no more water flow coming out of the system.
3. Check the pressure at the air port (the Shrader valve) in the top of the tank using a good tire gauge. It should be 2 PSI LESS than the Start pressure of your switch. If it is less than that, add air until you have 2 PSI less than the Start pressure you want to operate at. If the pressure is to high (unlikely), bleed it down to the correct setting.
You should check your tire gauge against the water pressure gauge on your system. When the pump is not running and water not running, check the air pressure in the tank. It should be the same as the pressure on your water tank gauge. If it is not the same, note the difference and use that when setting the tank pressure.
A good rough check without all of that procedure is to run water until the pump starts and then turn off the water and measure the time to pump shutoff. If that time is short, you probably need to add more air per the procedure above. The actual time of a properly set up tank will depend on your pump capacity, tank capacity, and pressure switch settings.