Numbers are approximate, stones are natural and vary in shape, density and size. Expect a some overlap.

Sold By: 1 lbs	Number Of Pieces	Unit Size
Tiny	350 to 500	4mm to 6mm
Mini	250 to 350	1/4" to 1/2"
X-Small	141 to 250	1/2'' to 3/4''
Small	61 to 140	3/4'' to 1''
Medium	24 to 60	7/8'' to 1 1/4''
Large	14 to 24	1 1/8'' to 1 1/2''
X-Large	6 to 14	1 1/2'' to 2 1/4''
XX-Large	4 to 6	1 3/4" to 3"

Sold By: 1/2 lbs	Number Of Pieces	Unit Size
Tiny	250 to 350	4mm to 6mm
Mini	130 to 250	1/4" to 1/2"
X-Small	70 to 130	1/2'' to 3/4''
Small	30 to 69	3/4'' to 1''
Medium	12 to 29	7/8'' to 1 1/4''
Large	6 to 12	1 1/8'' to 1 1/2''
X-Large	3 to 6	1 1/2'' to 2 1/4''

Sold By: 1/4 lbs	Number Of Pieces	Unit Size
X-Small	70 to 130	1/2'' to 3/4''
Small	30 to 69	3/4'' to 1''
Medium	12 to 29	7/8'' to 1 1/4''
Large	6 to 12	1 1/8'' to 1 1/2''

Sold By: 50g	Number Of Pieces	Unit Size
Mini	29 to 35	1/4" to 1/2"
X-Small	13 to 28	1/2'' to 3/4''
Small	8 to 12	3/4'' to 1''
Medium	4 to 7	7/8'' to 1 1/4''
Large	2 to 3	1 1/8'' to 1 1/2''

Exception for denser stones:

Hematite, Malachite, Garnet, Lodestone, Copper + others

Sold By: 1 lb	Number Of Pieces	Unit Size
X-Small	27 to 40	1/4" to 3/4"
Small	25 to 45	3/4" to 1"
Medium	18 to 24	7/8" to 1 1/4"
Large	12 to 17	1 1/8'' to 1 1/2''
X-Large	7 to 11	1 1/2'' to 2 1/4''