This is a classful IPv4 subnet calculator which allows you to easily visualize A, B or C class subnets with min/max host and broadcast IP addresses.
First enter desired IP v4 network address, and modify Net Mask END value, then click Calculate button to determine all possible subnets.

Input IP Address

auto-determined from input
Class A < 127
Class B < 191
Class C < 223

auto-determined from input

Difference between START and END net mask range is exponent to the power of 2.
For example:
24 = 16 subnets.