Radiotherapy is performed to kill cancer cells by using ionizing radiation. Treatment planning using ionizing radiation requires appropriate energy because different energy levels will result in different dose distribution. Percentage depth dose (PDD) is one of the parameters used to see dose distributions. One of the radiation sources that can be used is electron beams. It is usually used for irradiating cancer cells on or below the skin surface. This research uses the Particle and Heavy Ion Transport-code System (PHITS) soft- ware to simulate a Monte Carlo simulation. The radiation beam used is 1.0 × 106 particles of electron beam with energies of 8 and 12 MeV. The distance between the source and the phantom is 100 cm with a 10 × 10 cm2 phantom field size. The dose calculation is done in a cube-shaped water phantom with a size of 40 × 40 × 40 cm3. The PDD curve generated with energy variations shows that with different energy, there are differ ences in dose distribution. The greater the electron energy, the maximum depth will also increase.