Although standards varied over the ages, it was customary to set basic grades; grades for rice paddies and fields were given according to their merits, such as productivity, on three basic levels: high grade (very fertile rice paddy), medium grade and lower grade (worn-out rice paddy); rice paddies with better production than high grade were "superfine rice paddies" and those with worse production than lower grade were "bottom-ranked rice paddies."
時代によって基準は違うものの、生産高など田畠の優劣に応じて上田・中田・下田を基本としてその上に上々田、その下に下々田という等級を設置するのが通例であった。