Litter is a collective noun that encompasses a large variety of items, ranging from organic to synthetic, and from sharp to inert. Despite this, conversations and regulation on litter continue to group these items with little consideration towards the various levels of associated negative consequences. As a result, the Litter Impact Index (LII) was constructed to score individual items within indicators of toxicity, tenacity, threat and transportability (4T). The product of the index provides a clear visualisation of litter impact on a 0–100 point scale. As a result, it is found that litter items have varying degrees of adverse effects and cannot be considered equally impactful. This index is the first of its kind and was developed with the intention to inform sustainable waste practices, litter related policy, and packaging design by decreasing associated negative impacts.