According to "Kani rei" 官位令 (the law concerning the official rank) of the Taiho and the Yoro Ritsuryo codes, the Imperial princes of the Imperial family were graded in four ranks from "Ippon" to "Shihon" (First to Fourth Rank); other Shoo (princes who didn't receive any proclamation to be an Imperial Prince) were in fourteen ranks from Shoichii (Senior First Rank) to Jugoinoge (Junior Fifth Rank, Lower Grade); subjects were in thirty ranks from Shoichii to Shosoige (Lesser Initial Rank, Lower Grade).
大宝令・養老令のうち官位について定めた『官位令』によれば、皇族の親王は一品（いっぽん）から四品（しほん）までの4階、諸王は正一位から従五位下まで14階、臣下は正一位から少初位下（しょうそいげ）まで30階の位階がある。