<p>The models describing dry matter partitioning and allocation to various components within the individual trees would be important inputs for process-based individual tree growth models and simulation systems. This study presents the allometric and quadratic models fitted to the ratios of biomass data of various components (leaf, branch, stem, and root) of the individual tree against diameter at breast height (dbh). Data from twenty-seven <em>Alnus nepalensis</em> trees in mid-hill region of Nepal were used to develop the models. The most attractive fit statistics were found with the model of ratio of stem to leaf biomass (R² = 0.95), and similarly the models with the ratios of leaf to branch, leaf to above-ground, and leaf to total-tree biomass explained more than 90% variations. The results also showed that leaf, branch, above-ground and tree-total biomass amounts rapidly increased with increasing dbh. The ratios of leaf to branch, leaf to above-ground, leaf to total-tree, crown to total-tree, and root to total-tree biomass rapidly decreased with increasing dbh in earlier stage and gradually levelled off in the later stage. The models can be used for estimation of biomass of components of the individual tree. These models may also be useful inputs for process-based individual tree growth models which have been gaining the popularity in forest science in recent years.</p>