What is a customary scale? How does it relate to imperial and metric scales?

US Customary drawing scales are expressed in inches to feet ratios. Metric drawing scales are expressed in non-dimensional ratios.





US Customary Scale ------------------------ Close Metric Scale (NOT EXACT)


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1' = 1'-0" (Full Size) ------------------------ 1:1 (Full Size)


6" = 1'-0" (Half Size) ------------------------ 1:2 (Half Size)


3" = 1'-0" --------------------------- ------------- 1:4


1 1/2" = 1'-0" --------------------------- ------------- 1:8


1" = 1'-0" --------------------------- ------------- 1:10


3/4" = 1'-0" --------------------------- ------------- 1:20


1/2" = 1'-0" --------------------------- ------------- 1:25


3/8" = 1'-0" --------------------------- ------------- 1:30


1/4" = 1'-0" --------------------------- ------------- 1:50


3/16" = 1'-0" --------------------------- ------------- 1:80


1/8" = 1'-0" --------------------------- ------------- 1:100


3/32" = 1'-0" --------------------------- ------------- 1:125


1/16" = 1'-0" --------------------------- ------------- 1:200


1" = 10' --------------------------- ------------- 1:100


1" = 20' --------------------------- ------------- 1:250


1" = 30' --------------------------- ------------- 1:400


1" = 40' --------------------------- ------------- 1:500


1" = 50' --------------------------- ------------- 1:600


1" = 80' --------------------------- ------------- 1:1000


1" = 100' --------------------------- ------------- 1:1200


1" = 200' --------------------------- ------------- 1:2000


1" = 250' --------------------------- ------------- 1:3000


1" = 400' --------------------------- ------------- 1:5000


1" = 500' --------------------------- ------------- 1:6000


1" = 1000' --------------------------- ------------- 1:10000