Conversation so far:
when did england convert to the metric system
The British Imperial was used as the official system of measurement in Great Britain from 1824 until the adoption of the metric system in 1965.
when did france convert to the metric system
The metric system was officially adopted by the French government on 7 April 1795.

Question: what did france use before 1795
Self-contained rewrite: what did measurement system did france use before 1795