Subnetting (Part 1)

/25 - 128 address - 126 usable 
/26 - 64 address - 62 usable
/27 - 32 address - 32 usable
/28 - 16 address - 14 usable
/29 - 8 address - 6 usable
/30 - 4 address - 2 usable
/31 - 2 address - 0 usable (Just for a point to point device) (router to router)
/32 - 2 address - -1 usable (Just for a single device)
 
/25 - 2 subnets
/26 - 4 subnets
/27 - 8 subnets
/28 - 16 subnets
/29 - 32 subnets
/30 - 64 subnets
/31 - 128 subnets

subnets / CIDR


For the /26 you just have to plus the 64 (+64 +64 +64 +64) which is the available host for that CIDR.

Its the same with others just find the availabe host first. 

Look above

192.168.1.0/26 - .0 .64 .128 .192 - network address
               - .63 .127 .255 - gateway address
               - 1-62 | 65-126 | 129-191 | 193-254 - usable address
192.168.1.0/27 - .0 .32 .64 .96 - network address
               - 
192.168.1.0/28 - .0 .16 .32 .48 - network address
192.168.1.0/29 - .0 .8 .16 .24 - network address