Accurate determination of leaf dry mass is fundamental to estimating key functional traits such as leaf mass per area (LMA). However, the importance of balance readability (1 mg vs 0.1 mg) for trait precision has rarely been quantified. We simulated 20,000 leaves spanning 1–500 mg dry mass to assess how balance resolution influences LMA error. When measured with a 1 mg balance, small leaves (<10 mg) exhibited 4–13% error in LMA, whereas a 0.1 mg balance reduced this to <1%. For larger leaves (>20 mg), errors dropped below 1% for both balances. The results demonstrate that 0.1 mg resolution is critical for precise trait estimation in species with small leaves or when subtle interspecific differences are of interest. We recommend selecting balance readability relative to expected leaf mass, or pooling leaves to achieve >20 mg per sample. Such precision ensures consistency in trait-based ecological studies. By revealing that minor differences in balance readability can generate major errors in leaf functional traits, this study establishes measurement precision as a critical foundation for reliable ecological inference from the leaf to global ecosystem scales. This study is essential because even small inaccuracies in leaf mass measurements can generate significant hidden errors in trait estimates, influencing conclusions about plant strategies, community assembly, and ecosystem functioning.