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IP Lookup Tools Subnet / CIDR Calculator

Subnet and CIDR calculator

Enter an IP address and prefix (for example 192.168.10.77/26) to get the network address, broadcast address, usable host range, subnet mask and wildcard mask at once. IPv4 and IPv6 are supported.

Runs in your browser The addresses you enter are not sent to a server.

You can type a subnet mask instead of the prefix: 192.168.10.77 255.255.255.192. An address on its own counts as /32 (/128 for IPv6).

Result: 192.168.10.64/26

IPv4

Example calculation: 192.168.10.77/26. Enter your own address in the box above; the result here updates.

Entered address
192.168.10.77
CIDR notation
192.168.10.64/26
Network address
192.168.10.64
Broadcast address
192.168.10.127
First usable address
192.168.10.65
Last usable address
192.168.10.126
Usable host count
62
Total address count
64
Subnet mask
255.255.255.192
Wildcard mask
0.0.0.63
Prefix length
/26
Block type
Private network (RFC 1918)

Binary view

Address11000000.10101000.00001010.01001101
Mask11111111.11111111.11111111.11000000
Network address11000000.10101000.00001010.01000000

Bold: network bits · faded: host bits

Common prefixes (IPv4)

PrefixSubnet maskWildcard maskTotal addressesUsable hosts
/8255.0.0.00.255.255.25516,777,21616,777,214
/9255.128.0.00.127.255.2558,388,6088,388,606
/10255.192.0.00.63.255.2554,194,3044,194,302
/11255.224.0.00.31.255.2552,097,1522,097,150
/12255.240.0.00.15.255.2551,048,5761,048,574
/13255.248.0.00.7.255.255524,288524,286
/14255.252.0.00.3.255.255262,144262,142
/15255.254.0.00.1.255.255131,072131,070
/16255.255.0.00.0.255.25565,53665,534
/17255.255.128.00.0.127.25532,76832,766
/18255.255.192.00.0.63.25516,38416,382
/19255.255.224.00.0.31.2558,1928,190
/20255.255.240.00.0.15.2554,0964,094
/21255.255.248.00.0.7.2552,0482,046
/22255.255.252.00.0.3.2551,0241,022
/23255.255.254.00.0.1.255512510
/24255.255.255.00.0.0.255256254
/25255.255.255.1280.0.0.127128126
/26255.255.255.1920.0.0.636462
/27255.255.255.2240.0.0.313230
/28255.255.255.2400.0.0.151614
/29255.255.255.2480.0.0.786
/30255.255.255.2520.0.0.342
/31255.255.255.2540.0.0.122
/32255.255.255.2550.0.0.011

What is calculated?

  • Network address, broadcast address, first and last usable address
  • Total addresses and usable host count; the special rules for /31 and /32
  • Subnet mask, wildcard mask and prefix length
  • The block's type: private (RFC 1918), shared address space (CGNAT, RFC 6598), loopback, link-local, documentation or multicast
  • Binary view with network bits and host bits marked separately
  • Splitting the block into smaller blocks, VLSM planning by host needs and an "is this address in the block?" check

How do I read the result?

  • Usable hosts are the total minus two: the network address and the broadcast address are not given to hosts. A /31 (RFC 3021) has two usable addresses and a /32 has one.
  • If the address you typed has host bits set (192.168.10.77/26), the result shows the block that address belongs to (192.168.10.64/26).
  • The wildcard mask is the inverse of the subnet mask (255.255.255.192 → 0.0.0.63); it is used in access lists (ACLs).
  • IPv6 has no broadcast address. The first address of a subnet (interface identifier zero) is reserved for routers (the subnet-router anycast address, RFC 4291); the result shows only the first and last address. The standard prefix for a local network is /64.

Frequently asked questions

How many hosts is a /24?

256 addresses and 254 usable hosts, with the subnet mask 255.255.255.0. The network and broadcast addresses are not assigned to hosts.

What is the difference between a prefix and a mask?

They carry the same information: /26 is the prefix length (the first 26 bits are the network part) and 255.255.255.192 is the same number in dotted form. The mask bits must be contiguous; 255.0.255.0 is not a valid subnet mask.

Are the addresses I enter stored?

No. The calculation is done by the script on the page in your browser; the addresses are not sent to a server and are not kept in any list.

Why are addresses with leading zeros such as 010.1.1.1 rejected?

On some systems a leading zero means an octal number; 010 can be 8, not decimal 10. The notation is rejected so that you do not get a wrong result.