IP Address Today

Subnet calculator

Enter an IPv4 block in CIDR notation, or an address with its subnet mask, and get every derived value at once. Everything runs in your browser — nothing is sent to a server.

Try:
Network address
192.168.1.128/26
Subnet mask
255.255.255.192
Wildcard mask(ACLs)
0.0.0.63
Broadcast address
192.168.1.191
Usable host range
192.168.1.129 – 192.168.1.190
Usable hosts
62
Total addresses
64
Address type
Private (RFC 1918)

How subnetting works

An IPv4 address is 32 bits. The prefix length after the slash says how many of those bits identify the network; the rest identify the host within it. A /26 fixes the first 26 bits, leaving 6 host bits, so the block holds 26 = 64 addresses.

Because the split happens on bit boundaries, blocks always have a power-of-two size and always start on a multiple of that size. This is why 192.168.1.130/26 belongs to the subnet starting at 192.168.1.128 and not at 192.168.1.130 — 130 is not a multiple of 64.

Worked example: 192.168.1.130/26

  • Mask — 26 network bits gives 255.255.255.192.
  • Network — 130 rounded down to a multiple of 64 is 128, so the subnet is 192.168.1.128/26.
  • Broadcast — the last address in the block: 192.168.1.128 + 64 − 1 = 192.168.1.191.
  • Usable range — 192.168.1.129 to 192.168.1.190, which is 62 hosts.

IPv4 subnet mask reference

Every prefix length from /8 to /32, with its mask and host count.

IPv4 prefix lengths with subnet mask, total addresses and usable hosts
CIDRSubnet maskAddressesUsable hosts
/8255.0.0.016,777,21616,777,214
/9255.128.0.08,388,6088,388,606
/10255.192.0.04,194,3044,194,302
/11255.224.0.02,097,1522,097,150
/12255.240.0.01,048,5761,048,574
/13255.248.0.0524,288524,286
/14255.252.0.0262,144262,142
/15255.254.0.0131,072131,070
/16255.255.0.065,53665,534
/17255.255.128.032,76832,766
/18255.255.192.016,38416,382
/19255.255.224.08,1928,190
/20255.255.240.04,0964,094
/21255.255.248.02,0482,046
/22255.255.252.01,0241,022
/23255.255.254.0512510
/24255.255.255.0256254
/25255.255.255.128128126
/26255.255.255.1926462
/27255.255.255.2243230
/28255.255.255.2401614
/29255.255.255.24886
/30255.255.255.25242
/31255.255.255.25422
/32255.255.255.25511

Frequently asked

Why does a /24 have 254 usable hosts and not 256?
The first address in a block is the network address, which names the subnet itself, and the last is the broadcast address, which reaches every host on it. Neither can be assigned to a machine, so a /24 holds 256 addresses but only 254 usable ones.
Why does this calculator say a /31 has 2 usable hosts?
RFC 3021 allows a /31 on point-to-point links, where there is no need for a broadcast address because there is only one other device. Both addresses are usable. Most older calculators still report 0, which is wrong for the links /31 exists to serve.
What is a wildcard mask?
A wildcard mask is the bitwise inverse of the subnet mask: where the subnet mask has ones, the wildcard has zeros. Cisco access control lists and OSPF use it to say which bits must match, so a /24 subnet mask of 255.255.255.0 becomes a wildcard of 0.0.0.255.
Does the tool accept an address that is not the network address?
Yes. Give it 192.168.1.130/26 and it works out that the address sits in the 192.168.1.128/26 subnet, then reports that subnet's values. You do not have to know the network address in advance — that is usually what you are trying to find.

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