A large portion of the terrestrial vegetation carbon stock is stored in the above-ground biomass AGB of tropical forests, but the exact amount remains uncertain, partly due to the difficulty of making direct, whole-tree measurements. We harvested four large tropical rainforest trees (stem diameter: 0.6-1.2m, height: 30-46m, AGB: 3960-18584kg) in a natural closed forest stand in East Amazonia, and measured above-ground green mass, moisture content and woody tissue density. We found approximately 40% of green mass was water, and the majority of AGB was most often found in the crown, but varied from 42-62%. Woody tissue density varied substantially intra-tree, with both height and radius, but variations were not systematic inter-tree. Terrestrial lidar data were collected pre-harvest, from which volume-derived AGB estimates were retrieved. These estimates were more accurate than traditional allometric counterparts (mean tree-scale relative error: 3% vs. 15%). Error in lidar-derived estimates remained constant across tree size, whilst error in allometric-derived estimates increased up to 4-fold over the diameter range. Further, unlike allometric estimates, the error in lidar estimates decreased when up-scaling to the cumulative AGB of the four trees. Terrestrial lidar methods therefore can help reduce uncertainty in tree- and stand-scale AGB estimates, which would substantially advance our understanding of the role of tropical forests in the global carbon cycle.