Subnet Calculator (CIDR)
Type IPv4 CIDR notation (e.g. 192.168.1.0/24) and instantly see network address, broadcast, subnet mask, usable host range, and more.
How to Use
Use "ip/prefix" format. Examples: 192.168.1.0/24, 10.0.0.0/8, 172.16.5.42/22.
Network address, broadcast, subnet mask, wildcard mask, first/last usable host, total IPs, usable hosts, and class (A/B/C) are tabulated.
Use "Copy all" to grab the full breakdown. Drop into router configs, VPN setup, or DHCP ranges.
FAQ
What is CIDR?
Classless Inter-Domain Routing. In "192.168.1.0/24", the number after the slash (prefix length) tells how many bits are the network portion. /24 means 24 network bits and 8 host bits.
Why total − 2 for usable hosts?
In a typical subnet, the first IP is the network address and the last is the broadcast — both reserved. So usable = total − 2. Exceptions: /31 (RFC 3021, 2 IPs both usable) and /32 (single host).
What is the wildcard mask?
The bitwise NOT of the subnet mask. Used in Cisco ACLs. e.g., mask 255.255.255.0 → wildcard 0.0.0.255.
What about classful (A/B/C)?
IP classes (A=1–126, B=128–191, C=192–223 in the first octet) are largely historical now that CIDR replaced them. We show them for reference only.
Is anything sent to a server?
No. All math runs as bit operations in your browser; nothing leaves the page.
