Background: Postmortem interval estimation (PMI) is an important goal in forensic medicine. Aim: to estimate PMI using a scoring method for postmortem changes; hypostasis, rigidity and corneal turbidity in burn cases, potassium (K+) in vitreous humor (VH) and serum and compare accuracy of thanatochemistry and scoring method for postmortem changes in estimation of PMI. Methods: The study was conducted from May 2017 to May 2018, 50 burn cases where autopsy confirmed the cause of death as severe burns and another 50 control cases. Physical postmortem changes were assessed and numerically scored. The VH (K+) and serum levels were measured. Data were statistically analyzed and linear regression analysis was used to obtain equations for calculation of PMI. Results: All studied variables in the present study were significantly correlated with PMI; highest correlation coefficient in control and burn groups was for VH (K+) level, followed by corneal turbidity and serum K+ then rigidity in burn groups, but in control groups the highest correlation coefficient was for VH (K+) and serum levels, followed by rigidity then corneal turbidity and lastly hypostasis. All equations obtained from the present study can predict PMI but with different levels of accuracy. Conclusion: The scoring method for physical postmortem changes was proved to be more valuable in PMI estimation than thanatochemistry.