Abstract: Three methods have been described to calculate definite integrals whichare necessary for the trajectory calculations on the fringing fields of toroidalcondensers and magnetic fields. Results of calculation are given for variouselectrode and magnetic pole structures. In order to check the accuracy of both approximations, interpolation andpolynomial, the results are compared with those obtained by accurate method.They are very close to the accurate value. Finally, a method has presentedalso for the fringing field distribution measured experimentally in magneticfield.