About the IP Subnet Calculator
IP Subnet Calculator takes an IPv4 address and a prefix length such as /24 and works out everything about that subnet: the network address, the broadcast address, the first and last usable host, the number of usable hosts, the subnet mask and the wildcard mask. It also shows the address class, whether the address is private, public, loopback, link-local, multicast or reserved, and the binary form of the address and mask with the network bits in bold. A second panel splits the network into equal smaller subnets and lists each one. It works with IPv4 only, and everything is calculated in your browser.
Updated September 2026
How to use the IP Subnet Calculator
- 1Type an IPv4 address such as 192.168.1.10.
- 2Choose the prefix length (/24) or the matching subnet mask. The two stay in step.
- 3Read the results and copy any value with its Copy button.
- 4To divide the network, pick a longer prefix under Split into smaller subnets.
IP addresses, masks and CIDR
An IPv4 address is a 32-bit number, usually written as four decimal parts, such as 192.168.1.10. A subnet divides it into two parts: the network part, which is shared by every device on the subnet, and the host part, which is unique to each device. The subnet mask tells you where the split is.
CIDR notation writes the split as a slash and a number. In /24 the first 24 bits are the network. The calculator keeps the prefix and mask in step, so choosing either one updates the other.
Network, broadcast and usable hosts
The network address is the first address of the block, with every host bit set to zero. The broadcast address is the last, with every host bit set to one. Everything in between can be given to devices, so a normal subnet has two fewer usable addresses than it has in total.
Two small cases are treated specially. A /31 has no room for a network and broadcast address, so both addresses are usable, as allowed for point-to-point links. A /32 is a single host address.
Splitting a network
Plan your split from the biggest group of devices to the smallest, and leave room for growth.
- Choose a prefix longer than the current one, for example /26 for a /24.
- Each extra bit doubles the number of subnets and halves the size of each.
- The table lists network, first host, last host and broadcast for each subnet.
- Up to 256 rows are shown. A larger split still shows the true count.
- Copy all copies the table as tab-separated text for a spreadsheet.
Private and special ranges
Private ranges (10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16) are for use inside networks. Loopback addresses in 127.0.0.0/8 refer to your own device, and link-local addresses in 169.254.0.0/16 are self-assigned when no address is available. Multicast addresses start at 224.0.0.0, and 240.0.0.0 upwards is reserved.
The counts follow the usual rules. Some cloud providers reserve extra addresses in each subnet, for example the first few, and this calculator does not subtract them. To convert an address to another number base, see Number Base Converter, and to find out your own address, use What Is My IP. To see an address in bits use IP to Binary Converter, and the Binary Translator for text.
Features
- Network, broadcast, first and last host in one view
- Usable and total address counts
- Subnet mask, wildcard mask and CIDR notation
- Address class and type (private, public, loopback and more)
- Binary view with network bits highlighted
- Subnet splitter with a Copy all button
Frequently asked questions
How do I calculate a subnet?
Enter the IP address and choose the prefix length. The network address is the IP with all the host bits set to zero, and the broadcast address is the same with all the host bits set to one. The usable hosts are the addresses in between. The calculator does these steps for you.
What does /24 mean?
It is the prefix length: the first 24 bits of the address identify the network and the last 8 bits identify hosts on it. A /24 is the same as the subnet mask 255.255.255.0 and holds 256 addresses.
How many usable hosts are in a /24?
254. A /24 has 256 addresses, but the first is the network address and the last is the broadcast address, so two cannot be given to devices. A /30 gives 2 usable hosts, a /31 gives 2 for point-to-point links, and a /32 is a single host.
What is the difference between a subnet mask and a wildcard mask?
They are opposites. The subnet mask has ones for the network part, like 255.255.255.0. The wildcard mask has ones for the host part, like 0.0.0.255. Wildcard masks appear in some router access lists.
How do I split a network into smaller subnets?
Pick a longer prefix under Split into smaller subnets. Each extra bit doubles the number of subnets and halves their size. For example, splitting a /24 into /26 gives 4 subnets of 62 usable hosts each. Up to 256 subnets are listed, and the count shows the true total.
What are private IP ranges?
Three ranges are reserved for private networks: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. Addresses in them are not routed on the public internet. The calculator marks them as Private, and treats 100.64.0.0/10 shared address space as Public.
Does it support IPv6?
Not yet. Typing an IPv6 address shows a message asking for an IPv4 address.