In the era of sentencing guidelines, the punishment for traffickers is primarily based on the offenders’ culpability and the drug weight. Existing literature tend to focus on the issue of proportionality as it relates to the roles and culpability of offenders. However, little attention has been drawn to the quantity of drugs. England and Wales have incorporated offender roles into their sentencing guidelines, while Hong Kong uses drug tariffs strictly based on drug weight to calculate the starting point of a sentence. Using a novel equation called ‘the arithmetic starting point of sentence’, this study examines the starting sentence based on each gram of drugs by undertaking a comparative analysis of the respective jurisdictions. The results show that both jurisdictions have adopted sentencing guidelines that exhibit a logarithmic curve. This implies that the scale used to measure the quantity of drugs is disproportionate, penalising smaller quantities more harshly than larger quantities.