Subnetting /22 (Mask 255.255.252.0)

Subnetting a /22 starts with this calculator: it finds the /22 block that contains an IPv4 address and lists every /22 subnet inside a bigger network. A /22 subnet mask is 255.255.252.0, and each block holds 1,024 addresses, with 1,022 usable as hosts. The calculator runs in your browser, is free, and needs no sign-up. Enter an IP address and a parent network such as 10.20.0.0/16 to see the block, its host range, and a full table of subnets.

It also answers the usual netmask for /22 question: 255.255.252.0, or 0.0.3.255 as a wildcard.

The page lists every /22 inside a /16 or larger parent, so you can pick free blocks for a new site.

How to use the /22 subnet calculator

1. Type an IPv4 address into the IP address field. The starting example is 10.20.7.9.
2. Type the bigger network into Parent network (CIDR), such as 10.20.0.0/16. Its prefix must be /22 or shorter.
3. Read the primary results. The first line is the /22 block that contains your address, with its usable host range. For 10.20.7.9 it is 10.20.4.0/22, with hosts 10.20.4.1 to 10.20.7.254.
4. Find the line that reads “Subnet X of Y” to see where the block sits in the parent. For the default example, it is Subnet 2 of 64.
5. Scroll to the subnet table to see every /22 subnet in the parent, with its first host, last host and broadcast address.
6. Open More options and set Start the table at subnet number to move through the table. Typing 257 shows subnets 257 to 512.
7. Open How it was calculated under the result to see the formula and the values used.

Preset chips above the form load typical cases. Use Copy result, Copy link, Print / save as PDF or Reset as needed.

Example: in 10.20.0.0/16 the /22 blocks start at 10.20.0.0, 10.20.4.0, 10.20.8.0 and so on, every 4 in the third octet; there are 64 of them.

Copy link keeps the IP and parent in the address so you can share a block plan with a colleague.

What is the /22 subnet mask?

A /22 prefix keeps the first 22 bits of the address for the network and leaves 10 bits for hosts. Written out, the mask is 11111111.11111111.11111100.00000000, which is 255.255.252.0 in dotted decimal; the wildcard (inverse) mask used in router access lists is 0.0.3.255. Each /22 block holds 2^10 = 1,024 addresses. The first is the network address and the last is the broadcast address (RFC 950), so 1,022 are usable hosts.

How do you find the /22 subnet of an IP address?

The mask stops being 255 in the third octet, and the block size there is 256 − 252 = 4. Round that octet of the address down to a multiple of 4, keep the octets before it and set the octets after it to 0. For 10.20.7.9, the third octet is 7; 7 ÷ 4 rounds down to 1, and 1 × 4 = 4. The network is therefore 10.20.4.0/22, the usable hosts run from 10.20.4.1 to 10.20.7.254, and the broadcast address is 10.20.7.255.

How many /22 subnets fit in a larger network?

Each step of one bit doubles the count, so a /16 holds 2^(22 − 16) = 64 subnets of size /22. In 10.20.0.0/16 they start at 10.20.0.0 and go up in steps of 4 in the third octet, to 10.20.252.0/22; 10.20.4.0/22 is number 2. The table on this page lists them with their first host, last host and broadcast address, 256 rows at a time.

How does a /22 compare with the sizes next to it?

One bit shorter, a /21 doubles the block to 2,048 addresses (2,046 usable hosts); one bit longer, a /23 halves it to 512 addresses (510 usable hosts). Two neighbouring /22 blocks can be joined into one /21 only when the first of them starts on a multiple of 8 in the third octet — 10.20.0.0/21 contains 10.20.0.0/22, 10.20.4.0/22.

How is a /22 written in different configurations?

The same mask appears in several forms depending on the device or file: CIDR notation /22 (most routers, cloud consoles and firewalls), dotted decimal 255.255.252.0 (older interface settings, DHCP), hexadecimal 0xFFFFFC00 (some Unix tools such as ifconfig on BSD), and the wildcard 0.0.3.255 in router access lists and OSPF network statements. They all describe the same 1,024-address block.

Where is a /22 used?

A /22 is four /24s in one network (1,022 usable hosts), used for campus or data-centre segments and as a typical small allocation of public IPv4 space.

Worked examples

Calculated by the tool above with these values.

Frequently asked questions

What is the subnet mask for a /22?

255.255.252.0, with wildcard mask 0.0.3.255. In binary the mask is 11111111.11111111.11111100.00000000.

How many usable hosts does a /22 have?

1,022. A /22 has 1,024 addresses in total, and the network and broadcast addresses are not assigned to hosts.

How do I subnet a /22 into /24s?

A /22 holds four /24s. For 10.20.4.0/22 they are 10.20.4.0/24, 10.20.5.0/24, 10.20.6.0/24 and 10.20.7.0/24; the block always starts on a third octet that is a multiple of 4.

What is the first and last usable IP address in a /22?

The first usable address is the network address + 1 and the last is the broadcast address − 1. For 10.20.4.0/22 that is 10.20.4.1 to 10.20.7.254.

What does the warning about host bits mean?

The parent network you typed is not a network address (it has host bits set), so the calculator rounds it down to its network address and says so.

Is the calculator free, and is anything I type uploaded?

Yes, it is free, needs no sign-up, and every calculation runs in your browser; nothing you type is uploaded. Results may be used in any work, including commercial projects, without attribution.

Can I print or share a calculation?

Yes. Print / save as PDF gives a one-page record with the inputs, results, steps and date, and Copy link stores your inputs in the page address so the same calculation reopens later.

Related tools

• /29 subnet mask: Use it when you need the mask and host count for smaller /29 blocks.
• /27 subnet: Use it when you are splitting a network into /27 blocks.
• /23 subnet mask: Use it when you need the mask and block details for the next size up from /22.
• /16 subnet: Use it when you want to see the larger /16 network that contains many /22 blocks.
• Subnet cheat sheet: Use it for a quick reference of common masks and block sizes.
• Subnet calculator: Use it for any prefix length other than /22.