IP Subnet Calculator
Calculate network, broadcast, host range and mask from any CIDR block.
Accepts CIDR (10.0.0.1/8), an address with a dotted mask (10.0.0.1 255.0.0.0), or a bare address (defaults to /24).
192.168.1.0/24
- Network address
- 192.168.1.0
- Broadcast address
- 192.168.1.255
- First usable host
- 192.168.1.1
- Last usable host
- 192.168.1.254
- Usable range
- 192.168.1.1 – 192.168.1.254
- Subnet mask
- 255.255.255.0
- Wildcard mask
- 0.0.0.255
- Prefix length
- /24
- Total addresses
- 256
- Usable hosts
- 254
- Address class
- C
- Scope
- Private / reserved
Binary
- Network
- 11000000.10101000.00000001.00000000
- Mask
- 11111111.11111111.11111111.00000000
This address is in a private or reserved range and is not routable on the internet.
Split into smaller subnets
About the IP Subnet Calculator
Enter an IPv4 address with a CIDR prefix or a dotted netmask and get the whole picture: network address, broadcast address, the usable host range, wildcard mask, and the binary breakdown. Useful whenever you are carving up address space, writing a firewall rule, or checking whether two hosts are actually on the same network.
How to use it
- 1 Type an address in CIDR form such as 192.168.1.10/24.
- 2 Or paste an address and a dotted netmask separated by a space.
- 3 Read off the network, broadcast and usable host range.
- 4 Use the split option to divide the block into equal smaller subnets.
What it does
- Network, broadcast, first and last usable host
- Subnet mask, wildcard mask and prefix length
- Total addresses and usable host count
- Address class plus private and reserved range detection
- Binary view of the network and mask
- Correct RFC 3021 handling for /31 point-to-point links
- Split a block into equal smaller subnets
Frequently asked questions
Is my input sent anywhere?
No. Every calculation happens locally in your browser using JavaScript. Nothing you paste is uploaded, logged, or stored on a server, which makes the tool safe to use with production data, credentials, and customer records.
Why is the usable host count two fewer than the total?
The first address in a block identifies the network itself and the last is the broadcast address, so neither can be assigned to a host. A /24 therefore has 256 addresses but only 254 usable ones. The exceptions are /31 and /32, which are handled differently.
What is a /31 subnet used for?
Point-to-point links. RFC 3021 allows both addresses in a /31 to be assigned, because a link with exactly two endpoints has no need for a broadcast address. This saves two addresses per link compared with using a /30, which matters at scale on router interconnects.
What is a wildcard mask?
The bitwise inverse of the subnet mask — 0.0.0.255 where the netmask is 255.255.255.0. Cisco ACLs and OSPF network statements take a wildcard rather than a netmask, and mixing the two up is a classic source of rules that silently match nothing or everything.
Which address ranges are private?
RFC 1918 reserves 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 for private use. Also non-routable are 127.0.0.0/8 for loopback and 169.254.0.0/16 for link-local autoconfiguration. The calculator flags all of these.
Does it support IPv6?
Not yet — this calculator is IPv4 only. IPv6 subnetting works differently in practice: prefixes are almost always /64 for a LAN and the host count is too large to be meaningful, so the same table of results would not tell you much.