Diabetes Mellitus is a group of metabolic disorders characterized by rise in blood glucose level. The measurement of Glycated Hemoglobin has been widely used to monitor glycemic control in patients with diabetes mellitus which is also a best marker for monitoring long term complications. As the prevalence of diabetes is increasing day by day, it is mandatory to give importance for self-management. The objective of the present study was to compare the levels of estimated HbA1c with calculated HbA1c derived from a simple, cost effective mathematical formula by using fasting plasma glucose. The present study comprised of 66 fasting whole blood samples. All the samples were analyzed for Glycated hemoglobin and glucose, using this blood glucose level HbA1c was calculated by a formula, HbA = 2.6+0.03 × Blood glucose (mg/dl). Both estimated and calculated values of HbA1c were compared by dependent t-test. It was observed that the mean ± SD levels of Estimated HbA1c and Calculated HbA1c were 7.11±1.89 and 6.60±1.58 respectively. The p value was <0.05. Therefore the study concluded that, there exists a significant difference between the levels of estimated HbA1c and calculated HbA1c and thus this mathematical formula cannot be used interchangeably with estimated HbA1c.