Hi all, i'm trying to calculate solenoid force using this tool: http://www.daycounter.com/Calculators/Magnets/Solenoid-Force-Calculator.phtml I can't understand the ralation with A in the formula and also if this formula takes into account the lenght of solenoid. I explain better: If i have a solenoid with 2000 turns inner diameter of 10mm wire diameter of 0.1mm and solenoid lenght of 20mm i have 17.66 mH inductance. If i have a solenoid with 2000 turns inner diameter of 10mm wire diameter of 0.1mm and solenoid lenght of 10mm i have 31 mH inductance. I have more layers of wire in 10mm instead in 20mm and the force is higher. So, this calculator calculate on a single layer? so does not consider the length of solenoid? I need to calculate on a multiple layer solenoid. There is formula that from Magnetic B-field or Inductance i obtain force on a pice of metal that distant g(stroke)?