IP Subnet Calculator
Calculate network address, broadcast address, host range, and number of usable hosts for any IPv4 CIDR block.
What is an IP subnet calculator?
The IP subnet calculator takes a CIDR block (e.g., 192.168.1.0/24) and returns the network address, broadcast, host range, and netmask — the basics every network engineer computes daily.
Formula
The /N suffix means N bits of network prefix and (32−N) bits of host part. Network = IP AND mask. Broadcast = network OR ~mask. Usable hosts = 2^(32−N) − 2.
Worked example
192.168.1.0/24: network 192.168.1.0, broadcast 192.168.1.255, hosts .1 to .254, mask 255.255.255.0, 254 usable hosts.
How to use this calculator
- Enter a CIDR block in IP/N format.
- The calculator returns all subnet details.
Frequently asked questions
What's a /24, /16, /8?
/24 = 256 addresses (~254 usable). /16 = 65,536 addresses. /8 = 16,777,216 addresses. Each step doubles the host count.
Why subtract 2 for usable hosts?
The first address is the network address; the last is the broadcast address. Neither can be assigned to a host. Exception: /31 and /32 (point-to-point links) use both.
What's the difference between /24 and /23?
/24 = 254 usable hosts in one subnet. /23 = 510 usable hosts (combines two /24 subnets). Useful when you outgrow a single /24.
Can I use this for IPv6?
This calculator is IPv4 only. IPv6 uses a different notation (e.g., 2001:db8::/64) and much larger address space. Different math, different tools.