Bags of Cement needed?

[rufrufryder]

If I am making 4'x3' cement base for BBQ grill roughly 4" thickness, how many 60lbs or 80 lbs bags do I need?

[HayZee518]

ok you got to figure how many cu ft you need. 48" X 36" X 4". = 6912 cubic inches of mix
COVERAGE
Bag size Yield
40 lb. (18.1 kg) .30 cu ft. (.008 cu. m)
45 lb. (20.4 kg) .34 cu. ft. (.01 cu. m)
60 lb. (27.2 kg) .45 cu. ft. (.012 cu. m)
80 lb. (36.2 kg) .60 cu. ft.(.016 cu. m)
90 lb. (40.8 kg) .68 cu. ft. (.02 cu. m)

1728 cu in = 1 cu ft 6912 divided by 1728 equals 5 cu ft.

you'll need 8.5 rounded off to nine bags of 80 lb dry mix and 11.1 say 12 bags of 60 lb dry mix.