RULE OF THUMB

general or approximate principle, procedure or rule based on experience or practice as opposed to a specific, scientific calculation or estimate. —5th ACC Vol 2 Glossary (Final Approval 7/12/89), Random House Second Edition Unabridged Dictionary., —HEV Approved Glossary, —3rd South African unpublished Appr GLS (19.3.92)

general or approximate principle, procedure or rule based on experience or practice as opposed to a specific, scientific calculation or estimate.