Classical Dose Converter

What 三两 or 半升 meant when a formula was written — the modern textbook convention beside the historical range, with the sources for each.

Historical metrology, not a dosing recommendation. The range is what the unit weighed in that period; how a formula was decocted, divided and taken is a separate question, and the scholars cited disagree.

Metrology by period

One 两 and one 升 in each period, as ranges. The textbook column is the modern convention for reading that period's texts.

Period	1 两	1 升	Textbook 1 两
Eastern Han 东汉 25–220	13.8–15.6 g	≈ 200 mL	3 g
Wei–Jin 魏晋 220–420	13.8–14.6 g	≈ 200 mL	3 g
Tang 唐 618–907	13.8–13.9 g	≈ 200 mL	3 g
Song 宋 960–1279	40–41.3 g	≈ 702 mL	30 g
Ming 明 1368–1644	37.1–38.1 g	≈ 1035 mL	30 g
Qing 清 1644–1912	≈ 37.3 g	1035–1035 mL	30 g
Republic of China 民国 1912–1949	≈ 31.3 g	≈ 1000 mL	30 g
PRC (to 1979) 中华人民共和国 1949–1979	≈ 31.3 g	≈ 1000 mL	30 g