In this paper, the current-voltage (I-V) characteristic and volt-tesla (V-T) characteristic of diodes with a p-n junction under the appearance of a magnetic field are considered. Analysis of the experimentally obtained magnetic diodes I-V characteristic and V-T characteristic with p-n junction, new formulas were derived for calculating the I-V characteristic and V-T characteristics. Based on the developed theoretical formulas, new I-V and V-T characteristics were calculated and graphs were obtained. Theoretically obtained graphs were compared with the experimental ones and similarities were found. Theoretical expressions have been developed to calculate the theoretical I-V and V-T characteristics. Theoretically, they were based on two reasons and their consistency with experience was shown.