Nacionalni podatki o zunanji trgovini z okroglim lesom so pomembni z vidika mednarodnega poročanja in so sestavni del analiz tokov lesa. Namena raziskave sta izračun objektivnih nacionalnih pretvorbenih faktorjev za preračun podatkov o masi v podatke o neto volumnu (neto m3) in oblikovanje predloga enotnih faktorjev za glavne drevesne vrste. Kot osnovne podatke smo uporabili uradne podatke SURS za leta 2003-2006. Izračunani enotni pretvorbeni faktorji za najbolj zastopane drevesne vrste so: 0,77 t/m3 za smreko in jelko0,98 t/m3 za bukev in 1,12 t/m3 za hrast. Mednarodni pretvorbeni faktorji (FAO) so za Slovenijo prenizki in dajejo previsoke uradne podatke o zunanji trgovini. Metoda izračuna pretvorbenih faktorjev za zunanjetrgovinske podatke o okroglem lesu je univerzalna in ponovljiva. Predlagamo periodično preverjanje pretvorbenih faktorjev.National roundwood trade data are important for international reporting and are an integral and important part of roundwood flow analysis. The main objective of the study was to calculate objective national conversion factors for transformation of mass into cubic metres solid volume under bark (net m3) and to propose uniform factors for main tree species. Official trade statistics data for the 2003-2006 period were used as raw data. Uniform proposed conversion factors for spruce and fir combined, beech and oak are 0.77 t/m3, 0.98 t/m3, and 1.12 t/m3, respectively. International conversion factors proposed by FAO are too low for Slovenia and consequently give higher official trade statistics data. The used method for calculation of national roundwood conversion factors for trade statistics is universal and repeatable. We propose periodical review of conversion factors
