Accurate assessment of kidney function is crucial when medications that are excreted by the kidneys are used, to reduce their toxicity while maintaining their efficacy. Estimated glomerular filtration rate (eGFR) is underestimated in obese individuals when BSA correction is applied (as with, commonly used current CKD-EPI and MDRD equations), which may result in premature discontinuation of renally-excreted medications. In fact, when drug dosing is considered, the various regulatory bodies (Kidney Disease Improving Global Outcomes [KDIGO], European Medicines Agency [EMA] and Food and Drug Administration [FDA]) recommend a de-indexed eGFR (ml/min). De-indexing of eGFR should be considered in patients with moderate (BMI 35-40) to severe (BMI >40) obesity, to prevent unnecessary withholding or under-dosing of medications that are excreted by the kidneys. A Simple calculator is developed that provides calculated creatinine clearance (by Cockcroft-Gault formula) in ml/min, CKD-EPI eGFR in ml/min/1.73m2 and de-indexed GFR in ml/min. These three values on a single screen provides the health care provider a broader view of the individuals kidney function for optimizing drug therapy in such individuals.