IP / CIDR Calculator
Calculate the network address, broadcast address, subnet mask, wildcard mask, usable host range and host count for any IPv4 or IPv6 CIDR or IP/mask. Also checks whether IPs belong to a network, splits a network into subnets, and converts an IP range into the minimal list of CIDR blocks.
What is the IP / CIDR Calculator?
CIDR notation such as 192.168.1.0/24 describes an IP network as an address plus a prefix length (the number of network bits). This calculator works out everything that follows from it for IPv4 and IPv6, and adds three tools network engineers often need: membership checks, subnetting and range-to-CIDR conversion. All calculations run in your browser.
How to use
- Calculator tab: type into IP address / CIDR, or click one of the example chips. You can enter CIDR (192.168.1.130/26), an IP with a mask separated by / or a space (172.16.5.4 255.255.240.0), or a single address.
- Contains tab: list networks in Networks (CIDR, one per line) and addresses or CIDRs in IP addresses or CIDRs to check. Each line is marked Inside, Outside or Invalid; Copy results copies them as TSV.
- Subnets tab: enter a Network (CIDR) and choose a size in Split into. Each option shows how many subnets and hosts you get. Copy list copies the subnets.
- Range → CIDR tab: enter a Start address and End address (or paste "start - end" into the first field) to get the smallest set of CIDR blocks that covers exactly that range.
Each result in the Calculator tab has a copy button, and Split this network into subnets opens the Subnets tab with the current network.
Example: 192.168.1.130/26
| Field | Value |
|---|---|
| Network address | 192.168.1.128 |
| Broadcast address | 192.168.1.191 |
| Subnet mask | 255.255.255.192 |
| Wildcard mask | 0.0.0.63 |
| Usable host range | 192.168.1.129 - 192.168.1.190 |
| Usable hosts / total | 62 / 64 |
| Class / type | C / Private (RFC 1918) |
A binary view highlights the network bits and host bits. For IPv6 the calculator shows the compressed (RFC 5952) and expanded forms, the first and last address, the prefix mask, the total address count and the number of /64 subnets.
Range example: 192.168.0.5 - 192.168.0.20 becomes 192.168.0.5/32, 192.168.0.6/31, 192.168.0.8/29, 192.168.0.16/30 and 192.168.0.20/32.
Address types
The address type is detected from the IANA special-purpose registries: private (RFC 1918), shared address space / CGNAT (100.64.0.0/10), loopback, link-local, documentation, benchmarking, multicast, reserved and limited broadcast for IPv4; unique local (ULA), link-local, multicast, IPv4-mapped, NAT64, 6to4, Teredo, documentation and global unicast for IPv6.
FAQ
Why does a /31 show two usable hosts and no broadcast address?
/31 networks are treated as point-to-point links (RFC 3021), where both addresses are usable. A /32 is a single host.
Why is there no broadcast address for IPv6?
IPv6 does not use broadcast, so the last address of the block is shown instead.
Which inputs are rejected?
IPv4 parts with leading zeros (e.g. 010.0.0.1) and IPv6 zone IDs (e.g. fe80::1%eth0). The subnet list shows up to 1,024 rows, though the total count is always displayed.
Are my IP addresses sent anywhere?
No. Nothing is looked up online; the tool does not query DNS, WHOIS or geolocation services.