How to use
- Enter an IPv4 or IPv6 address with a CIDR prefix in IP address or CIDR.
- If you entered an address without a prefix, choose one from Prefix.
- Keep Show binary checked to see the IPv4 address, netmask and network in binary, with the network bits underlined.
- Choose a longer prefix in Split into to divide the network into smaller subnets.
- Click Download CSV to save the split subnet list.
Examples
Find the subnet for a home network device
192.168.1.10/24
Address: 192.168.1.10 Network: 192.168.1.0/24 Netmask: 255.255.255.0 Wildcard mask: 0.0.0.255 Broadcast: 192.168.1.255 First usable host: 192.168.1.1 Last usable host: 192.168.1.254 Total addresses: 256 Usable hosts: 254 Address type: Private (RFC 1918) Legacy class: C Integer: 3232235786 Hex: 0xC0A8010A Host bits are set. The network is 192.168.1.0/24.
Split a private /8 network into /16 subnets
10.0.0.0/8
Address: 10.0.0.0 Network: 10.0.0.0/8 Netmask: 255.0.0.0 Wildcard mask: 0.255.255.255 Broadcast: 10.255.255.255 First usable host: 10.0.0.1 Last usable host: 10.255.255.254 Total addresses: 16777216 (2^24) Usable hosts: 16777214 Address type: Private (RFC 1918) Legacy class: A Integer: 167772160 Hex: 0x0A000000 256 × /16 subnets 10.0.0.0/16 | 10.0.0.1 – 10.0.255.254 | 10.0.255.255 | 65534 … 10.255.0.0/16 | 10.255.0.1 – 10.255.255.254 | 10.255.255.255 | 65534
Inspect an IPv6 /48 address range
2001:db8::/48
Address: 2001:db8:: Expanded: 2001:0db8:0000:0000:0000:0000:0000:0000 Network: 2001:db8::/48 Prefix mask: ffff:ffff:ffff:: Address range: 2001:db8:: – 2001:db8:0:ffff:ffff:ffff:ffff:ffff Total addresses: 1208925819614629174706176 (2^80) Address type: Documentation (RFC 3849)
IPv4 subnet mask reference
Show the table for /0 – /32
| Prefix | Netmask | Wildcard | Addresses | Usable hosts |
|---|---|---|---|---|
| /0 | 0.0.0.0 | 255.255.255.255 | 4294967296 | 4294967294 |
| /1 | 128.0.0.0 | 127.255.255.255 | 2147483648 | 2147483646 |
| /2 | 192.0.0.0 | 63.255.255.255 | 1073741824 | 1073741822 |
| /3 | 224.0.0.0 | 31.255.255.255 | 536870912 | 536870910 |
| /4 | 240.0.0.0 | 15.255.255.255 | 268435456 | 268435454 |
| /5 | 248.0.0.0 | 7.255.255.255 | 134217728 | 134217726 |
| /6 | 252.0.0.0 | 3.255.255.255 | 67108864 | 67108862 |
| /7 | 254.0.0.0 | 1.255.255.255 | 33554432 | 33554430 |
| /8 | 255.0.0.0 | 0.255.255.255 | 16777216 | 16777214 |
| /9 | 255.128.0.0 | 0.127.255.255 | 8388608 | 8388606 |
| /10 | 255.192.0.0 | 0.63.255.255 | 4194304 | 4194302 |
| /11 | 255.224.0.0 | 0.31.255.255 | 2097152 | 2097150 |
| /12 | 255.240.0.0 | 0.15.255.255 | 1048576 | 1048574 |
| /13 | 255.248.0.0 | 0.7.255.255 | 524288 | 524286 |
| /14 | 255.252.0.0 | 0.3.255.255 | 262144 | 262142 |
| /15 | 255.254.0.0 | 0.1.255.255 | 131072 | 131070 |
| /16 | 255.255.0.0 | 0.0.255.255 | 65536 | 65534 |
| /17 | 255.255.128.0 | 0.0.127.255 | 32768 | 32766 |
| /18 | 255.255.192.0 | 0.0.63.255 | 16384 | 16382 |
| /19 | 255.255.224.0 | 0.0.31.255 | 8192 | 8190 |
| /20 | 255.255.240.0 | 0.0.15.255 | 4096 | 4094 |
| /21 | 255.255.248.0 | 0.0.7.255 | 2048 | 2046 |
| /22 | 255.255.252.0 | 0.0.3.255 | 1024 | 1022 |
| /23 | 255.255.254.0 | 0.0.1.255 | 512 | 510 |
| /24 | 255.255.255.0 | 0.0.0.255 | 256 | 254 |
| /25 | 255.255.255.128 | 0.0.0.127 | 128 | 126 |
| /26 | 255.255.255.192 | 0.0.0.63 | 64 | 62 |
| /27 | 255.255.255.224 | 0.0.0.31 | 32 | 30 |
| /28 | 255.255.255.240 | 0.0.0.15 | 16 | 14 |
| /29 | 255.255.255.248 | 0.0.0.7 | 8 | 6 |
| /30 | 255.255.255.252 | 0.0.0.3 | 4 | 2 |
| /31 | 255.255.255.254 | 0.0.0.1 | 2 | 2 |
| /32 | 255.255.255.255 | 0.0.0.0 | 1 | 1 |
/31 networks are point-to-point links (RFC 3021) with two usable addresses; /32 is a single host.
FAQ
Can I enter a subnet mask instead of CIDR notation?
For IPv4, enter the address and dotted netmask separated by a space or slash, such as 172.16.5.4 255.255.240.0. The mask must have contiguous 1-bits; a mask such as 255.0.255.0 is invalid.
How many usable IP addresses are in a /31?
An IPv4 /31 has two usable addresses for a point-to-point link under RFC 3021, with no broadcast address. A /32 represents a single host.
Why is there no broadcast address for IPv6?
IPv6 has no broadcast address. The calculator shows the full address range and total address count instead of separate broadcast and usable-host rows.
How many subnets can I split a network into?
You can split up to 16 bits beyond the original prefix, producing up to 65,536 subnets. The on-page table shows the first 1,024 rows; the CSV includes up to 65,536 rows.
Is my IP address uploaded or saved?
Calculations run in your browser, and the entered address is not uploaded. It is written into the URL hash, so it remains in browser history and copied links; options are saved in localStorage, but the address is not.