This article provides a comprehensive guide for dose conversion between animals and humans, emphasizing the importance of understanding interspecies allometric scaling in clinical pharmacology. The review covers the basic principles of dose translation and the estimation of starting doses for clinical trials using allometric scaling. It highlights that the common approach of scaling doses based solely on body weight is insufficient due to differences in biochemical, functional systems, and pharmacokinetics across species. The article discusses four methods for assessing initial doses: dose by factor, similar drug, pharmacokinetically guided, and comparative approaches. Allometric scaling, which considers body surface area, is highlighted as an empirical method that normalizes doses to account for differences in metabolic rate and pharmacokinetics. The US Food and Drug Administration (FDA) currently recommends the dose by factor approach, which uses no observed adverse effect levels (NOAELs) from preclinical studies to estimate human equivalent doses (HEDs). The article provides detailed steps for calculating the maximum recommended starting dose (MRSD) and includes equations and examples to illustrate the process. It also addresses the limitations of allometric scaling, such as the need to consider specific pharmacokinetic parameters and the suitability of certain drugs for this method. The conclusion emphasizes the importance of careful consideration of pharmacokinetic and pharmacodynamic differences among species and the utility of allometric scaling in dose extrapolation.This article provides a comprehensive guide for dose conversion between animals and humans, emphasizing the importance of understanding interspecies allometric scaling in clinical pharmacology. The review covers the basic principles of dose translation and the estimation of starting doses for clinical trials using allometric scaling. It highlights that the common approach of scaling doses based solely on body weight is insufficient due to differences in biochemical, functional systems, and pharmacokinetics across species. The article discusses four methods for assessing initial doses: dose by factor, similar drug, pharmacokinetically guided, and comparative approaches. Allometric scaling, which considers body surface area, is highlighted as an empirical method that normalizes doses to account for differences in metabolic rate and pharmacokinetics. The US Food and Drug Administration (FDA) currently recommends the dose by factor approach, which uses no observed adverse effect levels (NOAELs) from preclinical studies to estimate human equivalent doses (HEDs). The article provides detailed steps for calculating the maximum recommended starting dose (MRSD) and includes equations and examples to illustrate the process. It also addresses the limitations of allometric scaling, such as the need to consider specific pharmacokinetic parameters and the suitability of certain drugs for this method. The conclusion emphasizes the importance of careful consideration of pharmacokinetic and pharmacodynamic differences among species and the utility of allometric scaling in dose extrapolation.