In CIDR, you have a IP address followed by bit-length prefix separated by slash(/). Now you can start to convert bit-length prefix to quad-dotted by separating the bit-length prefix in increments of 8 and adding the final bit number.     Example:  If the bit-length prefix is 27, then write it as 8 + 8 + 8 + 3 .   Example:  If bit-length prefix is 12, then write it as 8 + 4 + 0 + 0 .   Example:  Default bit-length prefix is 32, then write it as 8 + 8 + 8 + 8. The total number of bits is represented using the following equation: Tb = 8. Subnet masks can be 0, 128, 192, 224, 240, 248, 252, 254 and 255.  The table above gives you the Number of bits used for subnetting (n) to their corresponding subnet mask.     For subnet mask 255 is default, so it'll not consider for subnet masking.   From the previous step, you got IP address = 170.1.0.0 and Sub-net mask = 255.255.255.192  Total bits = Tb = 8  Number of bits used for subnetting = n.  As the subnet mask = 192, its corresponding number of bits used for Subnetting is 2 from above table. The Number of subnets is 2n.    In our example, the number of subnets = 22 = 4.  The total number of subnets is 4. This is represented with the formula (Δ) = 2m.  In our example, the value of last bit used for subnet masking = Δ = 26 = 64. The value of the last bit used for subnet masking is 64. The number of hosts per subnet is 2m - 2. Now you can find previously calculated number of subnets by separating subnets each having the value of last bit used for subnet masking or Δ.   In our example, the last value used for subnet masking is 64. This produces 4 subnets with 64 addresses. Our example IP is 170.1.0.0. This falls in the 170.1.0.0 - 170.1.0.63 subnet.

Summary:
Write the bit-length prefix in bit format. Determine the total number of bits. Determine the number of bits used for subnetting. Calculate the number of subnets. Calculate the value of last bit used for subnet masking. Calculate the number of hosts per subnet. Separate the subnets by the value of the last bit used for subnet masking. Find which subnet your IP address is in.