IPv4 Subnet Calculator

Enter an IPv4 network block in CIDR notation, then choose a prefix, address capacity, or subnet count. The calculator shows network, broadcast, usable hosts, wildcard mask, and generated subnet ranges.

Network block and subnet size

Enter an IPv4 network block in CIDR notation, then choose a prefix, address capacity, or subnet count. The calculator shows network, broadcast, usable hosts, wildcard mask, and generated subnet ranges.

Enter an IPv4 address with a CIDR prefix, for example 192.168.1.0/24. Host bits are normalized to the network boundary.

Subnet details

Network address

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Usable-host range

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Broadcast address

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Wildcard mask

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CIDR prefix

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Subnet mask
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First usable host
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Last usable host
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Total IP addresses
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Usable hosts
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Block size / increment
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Address class
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Generated subnets

# CIDR Network Usable-host range Broadcast

No subnets to display yet.

What this tool does

This calculator analyzes IPv4 blocks in CIDR notation and derives their network address, broadcast address, host range, dotted-decimal mask, wildcard mask, and capacity.

Calculations run locally in your browser: the entered address and results are not sent to the server. This tool is for IPv4, not IPv6.

How to use the tool

  1. Enter an IPv4 address with its CIDR prefix, such as 192.168.1.10/24. Any host bits are automatically normalized to the network boundary.
  2. Then choose a prefix, required address capacity, or number of equal subnets. The calculator adjusts choices that are incompatible with the starting block.
  3. Review the network address, broadcast address, host range, masks, and total and usable address counts. You can copy result cards and table rows.
  4. To document a split, use the generated subnet table and its pagination controls.

Useful applications

  • Check connection or IPv4 configuration values before entering them in a router, firewall, or server.
  • Extract the network address, broadcast address, and host range from a CIDR block, then compare its capacity with a real requirement.
  • Spot a typo in a mask or prefix by checking whether block boundaries and calculated results are consistent.
  • Explain IPv4 network structure and plan equal-size subnet splits for learning or documentation.

Notes and limitations

  • An input such as 192.168.1.10/24 contains host bits, so it is normalized to 192.168.1.0/24 because the network address marks the block boundary.
  • For a conventional subnet, usable-host capacity is generally the total address count minus two: one network address and one broadcast address. The same rule does not apply in the same way to /31 and /32.
  • A /31 has two addresses that can be used as endpoints on a point-to-point link; a /32 has one address used as a host route. /0 covers all IPv4 and is omitted from the reference table.
  • Class A–E labels are shown as historical context. Modern routing and address allocation use CIDR prefixes, not those classes.
  • A wildcard mask is the complement of an IPv4 mask and is used in some filtering rules; it does not replace the CIDR mask when describing a network.

Frequently asked questions

What does the CIDR prefix after an IPv4 address mean?

The number after the slash tells you how many bits form the network part. A /24 reserves 24 bits for the network and leaves 8 bits for addresses in the block.

Why does the address sometimes change after I enter it?

If the address contains host bits, the calculator clears them to show the network’s actual boundary. For example, 192.168.1.10/24 becomes 192.168.1.0/24; this does not change a remote address.

How many hosts can an IPv4 /24 network hold?

A /24 contains 256 addresses. Under conventional subnetting, 254 are usable for hosts, from 192.168.1.1 through 192.168.1.254 in the familiar example; .0 is the network and .255 is the broadcast address.

Are the addresses in a /31 and /32 usable?

Yes, depending on context: both addresses in a /31 can serve as point-to-point endpoints, while a /32 identifies exactly one address or host route. Do not apply the “total minus two” formula blindly to these prefixes.

How do I split a /24 into four /26 subnets?

Borrow two host bits because 2² = 4. Each /26 block contains 64 addresses. The resulting networks are 192.168.1.0/26, .64/26, .128/26, and .192/26.

Reference

IPv4 mask reference and examples

This table lists the calculator’s available prefixes from /8 through /32. Masks and address counts are derived from each prefix so they remain consistent with the calculator.

CIDR prefix, dotted-decimal mask, and IPv4 block capacity
CIDR prefixDotted-decimal maskTotal addressesUsable 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 — 2 addresses on a point-to-point link
/32255.255.255.25511 — 1 address / host route

/0 covers all 4,294,967,296 IPv4 addresses. It is intentionally omitted from this compact reference to match the choices in the interface.

The “total addresses minus 2” convention applies to conventional subnets, but not universally to /31 and /32; their use determines how many addresses are usable.

1. Read 192.168.1.10/24

The normalized network address is 192.168.1.0 and the dotted-decimal mask is 255.255.255.0.

The broadcast address is 192.168.1.255; the conventionally usable host range is 192.168.1.1 through 192.168.1.254.

The block contains 256 addresses in total, of which 254 are conventionally usable for hosts.

2. Split a /24 into four /26 subnets

Two additional host bits are needed because 2² = 4 subnets, so the new prefix is /26.

Each /26 block contains 64 addresses. The four networks are 192.168.1.0/26, 192.168.1.64/26, 192.168.1.128/26, and 192.168.1.192/26.

3. Plan for at least 50 hosts

A /27 has 32 addresses in total, or 30 under the conventional usable-host count, so it is too small.

A /26 has 64 total addresses, or 62 conventionally usable hosts, making it the smallest block that meets a need for at least 50 hosts.

For a broader network diagnosis, you can also use:

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