IPv4 CIDR Calculator
Enter an IPv4 address with a prefix length to get the network, broadcast, first and last host, netmask, wildcard mask and the number of addresses in the block.
- Runs in your browser
- Free to use
About this tool
CIDR (Classless Inter-Domain Routing) notation describes a block of addresses with a starting address and a prefix length. This calculator expands any IPv4 CIDR into the numbers network engineers need every day: the network address, the broadcast address, the first and last usable host, the dotted and binary netmask, the wildcard mask and the total and usable host counts, plus the decimal form of the boundaries for database queries.
It also tells you the classful letter of the range and whether it falls in a private RFC 1918 block. For the reverse question, "is this address inside that range?", use the IPv4 CIDR Checker; for IPv6 blocks use the IPv6 CIDR Calculator.
How to use it — quick steps
- 01
Enter the ipv4 cidr
Type or paste the ipv4 cidr in the field above, for example 192.168.10.0/24.
- 02
Press "Calculate subnet"
Press "Calculate subnet" or Ctrl + Enter. The result appears instantly below the form.
- 03
Read the result
It appears in the dark panel under the form instantly. Every block has [copy] and other actions.
Key features of this tool
Nothing leaves your browser
The processing is plain JavaScript that runs on your device: the text you paste is never uploaded to our servers or to anyone else.
Instant results
Results appear the moment you press the button, even for long inputs, and every block has copy and download actions.
Works everywhere
No installation, no account and no limits: the tool works on desktop and mobile, in any modern browser, as often as you like.
Frequently asked questions
What does the /24 in a CIDR mean?
The number of leading bits that identify the network. /24 leaves 8 bits for hosts, so the block has 256 addresses (254 usable). Each step down (/23, /22…) doubles the size.
Why are two addresses not usable?
In blocks of /30 and larger the first address identifies the network and the last is the broadcast address. /31 blocks are used for point-to-point links where both addresses are usable, and /32 is a single host.
What is the wildcard mask?
The inverse of the netmask, used by Cisco ACLs and some firewalls: 0 bits must match, 1 bits are "don't care".
Is the calculation done on your servers?
No, everything happens in your browser with 32-bit integer maths; the address is never sent anywhere.