CIDR Subnet Calculator
Type a network in CIDR notation and get its network address, broadcast, usable host range, masks and counts. IPv4 and IPv6, entirely in your browser.
Result
- Network
- 192.168.1.0/24
- Netmask
- 255.255.255.0
- Wildcard mask
- 0.0.0.255
- Broadcast address
- 192.168.1.255
- Usable host range
- 192.168.1.1 to 192.168.1.254
- Usable hosts
- 254
- Total addresses
- 256
- Netmask (binary)
- 11111111.11111111.11111111.00000000
How CIDR notation works
CIDR (Classless Inter-Domain Routing) writes a network as an address plus a prefix length: 192.168.1.0/24 means "the first 24 bits identify the network, the remaining 8 identify hosts inside it". Fewer prefix bits means a bigger network: each step down doubles the address count. The first address in an IPv4 block is the network address and the last is broadcast, which is why a /24 has 256 addresses but 254 usable hosts. The two exceptions are /31 (RFC 3021 point-to-point links use both addresses) and /32 (a single host route).
Common IPv4 prefix sizes
| Prefix | Netmask | Usable hosts | Typical use |
|---|---|---|---|
| /8 | 255.0.0.0 | 16,777,214 | Legacy class A block |
| /16 | 255.255.0.0 | 65,534 | Large private network (10.x, 172.16.x) |
| /22 | 255.255.252.0 | 1,022 | Mid-size allocation |
| /24 | 255.255.255.0 | 254 | The classic LAN / smallest common BGP announcement |
| /27 | 255.255.255.224 | 30 | Small server subnet |
| /29 | 255.255.255.248 | 6 | Typical ISP customer block |
| /30 | 255.255.255.252 | 2 | Point-to-point link (classic) |
| /31 | 255.255.255.254 | 2 | Point-to-point link (RFC 3021) |
| /32 | 255.255.255.255 | 1 | Single host route |
IPv6 prefixes in practice
IPv6 uses the same notation over 128 bits, and the numbers get large fast: a /64, the standard size for a single LAN segment, contains 264 addresses. ISPs commonly delegate a /56 or /48 to a site, which is 256 or 65,536 separate /64 networks. There is no broadcast address in IPv6, so this calculator shows the first and last addresses of the block instead. It also accepts compressed forms (2001:db8::1) and expands them for you.
Where you meet CIDR when using proxies
Proxy and scraping work runs into CIDR often: whitelisting a provider's exit ranges in a firewall, checking whether two proxy IPs sit in the same subnet, or reading "a /24 of dedicated IPs" and knowing that means 254 usable addresses on distinct last octets. Two addresses in the same /24 are often treated alike by a target, so the spread of a plan's addresses across subnets is one thing to check when comparing proxy plans.
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