Subnet Calculator
Free online subnet calculator tool, network range from IP/CIDR
What is CIDR Notation?
CIDR (Classless Inter-Domain Routing) notation specifies an IP address range using an IP address followed by a slash and the number of network bits. For example, 192.168.1.0/24 represents a network with 256 addresses (192.168.1.0 to 192.168.1.255). CIDR replaced the older classful network addressing system.
How to Calculate Subnet Information
Enter an IP address with CIDR prefix (e.g. 10.0.0.0/24). The tool calculates and displays: network address, broadcast address, subnet mask, first and last usable host addresses, and total number of hosts.
▶What does /24 mean in CIDR?
The /24 prefix means the first 24 bits are the network portion, leaving 8 bits for hosts. This gives 2^8 = 256 total addresses (254 usable hosts, minus network and broadcast addresses).
▶What is the difference between network address and broadcast address?
The network address is the first address in a subnet (all host bits are 0). The broadcast address is the last address (all host bits are 1). Neither can be assigned to a host device.
▶How many addresses does a /28 subnet have?
A /28 subnet has 4 host bits, giving 2^4 = 16 total addresses (14 usable hosts after subtracting network and broadcast addresses).