Subnet Calculator (IPv4)

Free IP subnet calculator and CIDR calculator. Enter an IP address and a prefix (or type it as 192.168.1.10/24) to get the network, broadcast, host range and masks instantly.

Binary view

Red bits are the network part; grey bits are the host part.

Split this network into smaller subnets

🔒 Runs in your browser. Nothing you type is sent or stored.

How to use the subnet calculator

  1. Type an IPv4 address, for example 192.168.1.10. You can also type it with a prefix, like 192.168.1.10/26, or with a mask, like 192.168.1.10 255.255.255.192.
  2. Pick the subnet mask or CIDR prefix from the list (skip this if you typed it).
  3. Press Calculate. Use Copy link to share the exact result.

What the results mean

  • Network address – the first address in the subnet. It identifies the network and is not given to a device.
  • Broadcast address – the last address. Traffic sent here reaches every host on the subnet.
  • Usable host range – the addresses you can assign to devices, between the network and broadcast addresses.
  • Subnet mask – marks which bits belong to the network (1s) and which to hosts (0s).
  • Wildcard mask – the inverse of the subnet mask, used in Cisco ACLs and OSPF.

Worked example: 192.168.10.77/27

A /27 leaves 5 host bits, so each subnet has 25 = 32 addresses. Subnets start every 32 addresses in the last octet: 0, 32, 64, 96… The address 77 falls in the block that starts at 64.

  • Network: 192.168.10.64
  • Broadcast: 192.168.10.95
  • Usable hosts: 192.168.10.65 to 192.168.10.94 (30 hosts)
  • Mask: 255.255.255.224, wildcard 0.0.0.31

Subnet mask cheat sheet

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

/31 networks are used for point-to-point links (RFC 3021) and /32 represents a single host.

Private IP address ranges

RangeCIDRAddresses
10.0.0.0 – 10.255.255.25510.0.0.0/816,777,216
172.16.0.0 – 172.31.255.255172.16.0.0/121,048,576
192.168.0.0 – 192.168.255.255192.168.0.0/1665,536

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Frequently asked questions

What is a subnet calculator?

A subnet calculator takes an IP address and a prefix length (or subnet mask) and works out the network address, broadcast address, usable host range and number of hosts for that subnet.

How many usable hosts are in a /24?

A /24 has 256 addresses. Two are reserved (the network and broadcast addresses), so 254 are usable for hosts.

What is the difference between a subnet mask and CIDR notation?

They describe the same thing. 255.255.255.0 and /24 both mean the first 24 bits are the network part. CIDR is just a shorter way to write the mask.

What is a wildcard mask?

A wildcard mask is the inverse of the subnet mask (for /24, 0.0.0.255). It is used in Cisco ACLs and OSPF configuration to say which bits to ignore.

Why does a /31 have 2 usable hosts?

Normally the first and last addresses are reserved. RFC 3021 allows /31 networks on point-to-point links, where both addresses can be used and no broadcast address is needed.

Is my IP address sent anywhere when I use this tool?

No. All calculations run in your browser with JavaScript. Nothing you type is sent to a server or stored.