CIDR Calculator
Parse any IPv4 CIDR block and get the netmask, wildcard, network and broadcast addresses, first and last usable host, total host count, and classification (private, public, loopback, multicast). All computed locally.
192.168.1.0/24255.255.255.00.0.0.255192.168.1.0192.168.1.255192.168.1.1192.168.1.25425625411000000.10101000.00000001.00000000 → 11000000.10101000.00000001.11111111
About the CIDR Calculator
This free online CIDR (Classless Inter-Domain Routing) calculator takes any IPv4 CIDR block and returns the netmask, wildcard, network and broadcast addresses, first and last usable host, total host count, and RFC-1918 classification. Perfect for subnetting homework, VPC design, firewall rule review, and network troubleshooting.
What CIDR Notation Means
CIDR writes an IPv4 subnet as network/prefix, where the prefix is the number of leading 1-bits in the netmask. For example, 192.168.1.0/24 covers 256 addresses with mask255.255.255.0; the first and last are reserved for the network and broadcast, leaving 254 usable host addresses.
Common Prefixes
/8— 16 777 216 addresses (whole Class A range)/16— 65 536 addresses (whole Class B range)/24— 256 addresses (typical LAN segment)/28— 16 addresses (small VPC subnet)/30— 4 addresses (point-to-point link)/31— 2 addresses (RFC 3021 point-to-point, no broadcast)/32— single host route
Private vs Public Ranges
- RFC 1918 Class A:
10.0.0.0/8 - RFC 1918 Class B:
172.16.0.0/12 - RFC 1918 Class C:
192.168.0.0/16 - Loopback:
127.0.0.0/8 - Link-local (APIPA):
169.254.0.0/16 - Multicast:
224.0.0.0/4
Frequently Asked Questions
Why do /31 and /32 report different host counts?
A /32 is a single-host route — one address, no broadcast. A/31 under RFC 3021 is used for point-to-point links and treats both addresses as usable (no broadcast reservation). Classic subnets of/30 and larger lose two addresses to the network and broadcast reservations.
Is this calculator aware of my local timezone or network?
No. It operates on the input text only. Nothing is probed, resolved, or sent to a server.
Does it handle IPv6?
Not yet — this release covers IPv4 subnets. IPv6 planning typically uses/64 or shorter prefixes with a different allocation model.
Related Tools
Convert IP addresses to binary and back with the Number Base Converter. Comparing config files with CIDR entries? The JSON Diff tool is handy.
Full subnet info
Netmask, wildcard, network, broadcast, host range, and host count.
Live parsing
Updates instantly as you type; one-click presets for common blocks.
Fully private
Nothing is probed or sent — safe for internal VPC and firewall notes.