• One "square" of roof area is equivalent to 100 square feet.
• Slate is usually quantified in squares. (126 square feet of roof area = 1.26 squares).
• Standard slate lengths range from 12" to 24" tall. Larger sizes have greater coverage and require fewer pieces to cover one square then smaller sizes.
• The calculation for determining the number of pieces per square assumes a 3" headlap as a point of reference.

Common Roof Slate Sizes and the Number of Pieces Required To Cover One Square using Standard 3" Headlap
(h x w)	Pc/ sq		(h x w)	Pc/ sq		(h x w)	Pc/ sq		(h x w)	Pc/ sq		(h x w)	Pc/ sq		(h x w)	Pc/ sq
24 x 16	86		20 x 16	106		18 x 16	120		16 x 16	138		14 x 14	187		12 x 12	267
24 x 14	98		20 x 14	121		18 x 14	137		16 x 14	158		14 x 12	218		12 x 10	320
24 x 12	114		20 x 12	141		18 x 12	160		16 x 12	185		14 x 11	238		12 x 9	356
22 x 16	95		20 x 11	154		18 x 11	175		16 x 11	201		14 x 10	262		12 x 8	400
22 x 14	108		20 x 10	169		18 x 10	192		16 x 10	222		14 x 9	291		12 x 7	457
22 x 12	126					18 x 9	213		16 x 9	246		14 x 8	327		12 x 6	533
22 x 11	138								16 x 8	277		14 x 7	374
Pieces per square can be calculated by using the formula: 14,400/[((Length-Headlap)/2) x Width]
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