Network 192.168.1.0 Broadcast 192.168.1.255 First host 192.168.1.1 Last host 192.168.1.254 Netmask 255.255.255.0 Wildcard 0.0.0.255 Usable hosts 254 Total addresses 256 Prefix /24
About Subnet Calculator — IPv4 CIDR, Mask & Host Range
A subnet calculator turns an IPv4 CIDR block like 192.168.1.0/24 into the numbers you actually need: the network and broadcast addresses, the usable host range, the subnet mask, the wildcard mask, and the host count. It saves you from error-prone binary math when you're carving up an address space, sizing a VLAN, or writing a firewall rule.
This free CIDR calculator does pure 32-bit address arithmetic in your browser. There's no DNS lookup, no ping, and nothing is sent to a server — type a block and the full breakdown updates instantly, completely offline.
It also handles the edge cases correctly, including /31 point-to-point links (RFC 3021) and /32 single hosts, so the usable-host count is always right.
Features
- Network, broadcast, first and last usable host from any IPv4 CIDR
- Subnet mask and wildcard (inverse) mask in dotted-quad form
- Correct host counts, including /31 (RFC 3021) and /32 edge cases
- Pure address math — runs entirely offline, nothing leaves your browser
How to use
- Type an IPv4 CIDR block into the input, e.g. 192.168.1.0/24.
- Read the network, broadcast, host range, masks, and counts in the output.
- Copy any value with its copy button, or copy the whole breakdown at once.
Frequently asked questions
What is a CIDR block?
CIDR (Classless Inter-Domain Routing) notation writes an IP network as an address plus a prefix length, like 192.168.1.0/24. The /24 means the first 24 bits are the network portion, leaving 8 bits — 256 addresses — for hosts.
Why are there fewer usable hosts than total addresses?
In a normal subnet the first address is the network identifier and the last is the broadcast address, so neither can be assigned to a host. A /24 has 256 addresses but 254 usable ones. The exceptions are /31 and /32.
How do /31 and /32 work?
A /31 is a point-to-point link (RFC 3021): it has just two addresses and both are usable, with no separate broadcast. A /32 describes a single host — one address, used for loopbacks, host routes, and ACL entries.
What is the wildcard mask?
The wildcard mask is the bitwise inverse of the subnet mask (for /24, 0.0.0.255). It is mainly used in Cisco ACLs and OSPF, where a 1 bit means "match any" rather than "must match".
How many hosts are in a /24, /22, or /16?
A /24 has 256 addresses and 254 usable hosts, a /22 has 1,024 addresses and 1,022 usable, and a /16 has 65,536 addresses and 65,534 usable. Each smaller prefix doubles the address count: every bit you drop from the prefix doubles the hosts. Enter any block above to see the exact counts.
Is my input sent anywhere?
No. The calculation is pure 32-bit arithmetic performed locally in your browser. There are no network requests, no DNS, and no logging — it works fully offline.
Related tools
Everything runs locally in your browser — your input is never uploaded.