How it works
Type an IPv4 address with a CIDR prefix or a dotted mask. The tool ANDs the address with the mask to find the network, ORs it with the wildcard to find the broadcast, and counts the host bits for the size. A /31 keeps both addresses usable (point-to-point links, RFC 3021) and a /32 is a single host.
192.168.1.10/24 → network .0 · broadcast .255 · 254 usable hosts
Reading the result
- Network / broadcast: the first and last address of the block. Neither is usable on ordinary subnets (/30 and larger).
- Usable range: the addresses you can actually assign, from first to last.
- Wildcard: the inverse of the mask, used in firewall rules and access lists.
- Class and type: the historic A–E class plus whether the block is private (RFC 1918), loopback or link-local.
Tips
- Splitting a /24 into 4 gives four /26 blocks (.0, .64, .128, .192) of 62 usable hosts each.
- If the address you typed is not the network address (for example .10 in a /24), the result still shows the block it belongs to.
- Everything runs in your browser; nothing is uploaded.
Standards and sources
- Classless addressing (CIDR): RFC 4632; 32-bit masks: RFC 950
- /31 point-to-point links: RFC 3021; private addresses: RFC 1918
Last reviewed October 12, 2026
Frequently asked questions
What is the difference between network and broadcast?
The network address is the first address of a block and the broadcast is the last. On ordinary subnets neither can be assigned to a device; usable addresses run from first to last between them.
How many hosts fit in a /24?
256 addresses total, 254 usable. Each bit you add to the prefix halves the block: /25 holds 126 usable, /26 holds 62, down to /30 with 2 and /31 with 2 for point-to-point links.
What is the wildcard mask used for?
It is the inverse of the subnet mask (255.255.255.0 becomes 0.0.0.255) and is used in firewall rules and router access lists to describe which addresses a rule covers.
What does it mean when my address is not the network address?
Nothing is wrong: typing 192.168.1.10/24 simply shows the /24 block that .10 belongs to, with .0 as network and .255 as broadcast.