IP Subnet Calculator
IPv4 CIDR math: network, broadcast, usable host range, total hosts — with binary masks shown.
Calculate IPv4 subnet details from CIDR notation: network and broadcast addresses, usable host range, total hosts, subnet and wildcard masks, class, and the binary representations. Perfect for network engineers and devops work.
How to use the IP Subnet Calculator
- Enter an address in CIDR form (192.168.1.37/24) or with a full mask.
- Read network, broadcast, usable range and host count instantly.
- Check the binary mask and class for documentation.
Frequently asked questions
What is a /24 subnet?
A /24 has a mask of 255.255.255.0, giving 256 addresses — 254 usable hosts after the network and broadcast addresses. Enter any /24 above to see it.
How many hosts are in a /16?
65,536 addresses total, 65,534 usable. The usable count is 2^(32-prefix) - 2.
What is the network address?
The first address of the subnet, where the host bits are all zero. Devices don't use it; it identifies the subnet itself.
What is CIDR?
Classless Inter-Domain Routing — the slash notation that replaced fixed address classes, letting networks be any size from /0 to /32.
Fun facts about IP Subnet Calculator
- CIDR (Classless Inter-Domain Routing) replaced the old classful addressing system in 1993, allowing more efficient allocation of IP addresses.
- A /24 subnet contains 256 IP addresses (254 usable), while a /16 subnet contains 65,536 addresses — each additional bit doubles the size.
- The subnet mask 255.255.255.0 (/24) is the most common subnet size for small office and home networks.
- Private IP ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) are reserved for internal networks and are not routable on the public internet.
- A single /64 IPv6 subnet holds 2^64 ≈ 18.4 quintillion addresses: exactly the size of the whole IPv4 address space squared.