AIM: The aim of the present study was to estimate Eichhornia crassipes biomass by a non-destructive method that uses allometric measurements of foliar structures; METHODS: Aquatic macrophytes collected at different growth in a wetland were allometrically measured as (a) limbo length and width (b) petiole width and diameter. The same leaves were used to determine biomass, expressed in dry weight, after drying in an oven at 70 °C until constant weight; RESULTS: The correlation between petiole length/diameter with foliar biomass was r2 = 0.7705; p < 0.001, and between limbo width/length and foliar biomass was r2 = 0,8838; p < 0,001. It was shown that limbo width/length and petiole length/diameter are related to biomass. Two estimation models were built to estimate aerial biomass based on allometric and biomass data; CONCLUSION: Biomass values obtained with the model proposed in this study are similar to those obtained when the material was dried in the oven, as determined by the t test. The biomass determination model proposed in the present study was shown to be efficient, and allows the follow-up of plant growth in time.