The SEC prescribed a ratio for the barrel of oil equivalent (BOE) for natural gas of six thousand cubic feet (Mcf) per barrel of crude oil (Bbl). The 6:1 standard is based on thermal equivalence or gross heating values.To convert a thousand cubic feet (Mcf) of natural gas to barrels of oil equivalent (boe), divide by 6. For example, 600 Mcf = 100 Bbl.