Umbu (Spondias tuberosa Arruda, Anacardiaceae) is a fruit species native to the semi-arid region of Brazil and economically important for several regions. The objective of this study was to determine equations to estimate the leafiet area of S. tuberosa genotypes. A total of 1,000 leafiets was collected from four genotypes (250 leafiets of each genotype) of S. tuberosa. In each leafiet collected, the length, width, and leafiet area were measured, and the product between length and width was calculated. Linear, linear with intercept, power, and exponential regression models were used to fit the equations. The criteria for choosing the best equation were based on Pearson's correlation coefficients, Akaike's information criteria, Willmott's concordance indices, and root mean square error. The product-adjusted equations between length and width can be used to estimate the leafiet area of all S. tuberosa genotypes. The leafiet area of the species (pooled data) can be estimated accurately and quickly from equations obtained with the linear models without intercept (ŷ = 0.6911*LW) and power (ŷ = 0.7127*LW0.9888).