Determination of the required sample size is an important step in the planning of any research study. A large number of commercial and online resources are readily available for calculation of sample size required for various research designs. However, this abundance of information, the complexity, and the variation in calculation formulations and terminology used make it more confusing to researchers, particularly those with limited statistical knowledge. Therefore, there is a need for more simplified, easy to implement formulas for calculation of sample size. Here, we present a short review of the rules for calculation of sample size for common experimental designs used in research and provide more simplified forms for some of these formulas. Also, data are presented on sample size required for various scenarios with the intent to provide guidelines for researchers. A simple-to-use Excel sheet was developed to perform sample size calculations and is available online as a supplementary file. This Excel sheet was used to generate the data presented in this publication

Determination of the required sample size is an important step in the planning of any research study. A large number of commercial and online resources are readily available for calculation of sample size required for various research designs. However, this abundance of information, the complexity, and the variation in calculation formulations and terminology used make it more confusing to researchers, particularly those with limited statistical knowledge. Therefore, there is a need for more simplified, easy to implement formulas for calculation of sample size. Here, we present a short review of the rules for calculation of sample size for common experimental designs used in research and provide more simplified forms for some of these formulas. Also, data are presented on sample size required for various scenarios with the intent to provide guidelines for researchers. A simple-to-use Excel sheet was developed to perform sample size calculations and is available online as a supplementary file. This Excel sheet was used to generate the data presented in this publication