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Subnet Calculator — IPv4, IPv6 & CIDR

Calculate IPv4 and IPv6 network ranges, masks, and host counts with correct /31 and /32 handling. Client-side only.

Examples

Network address

192.168.1.0

Broadcast address

192.168.1.255

Usable hosts

254

Subnet mask

255.255.255.0

/24

Subnet range (192.168.1.0/24)

192.168.1.0192.168.1.1192.168.1.254192.168.1.255
Network (1)Usable host range (254)Broadcast (1)

Network details

Network
192.168.1.0
CIDR notation
/24
Subnet mask
255.255.255.0
Wildcard mask
0.0.0.255
First usable
192.168.1.1
Last usable
192.168.1.254
Total addresses
256
Usable hosts
254
Classification
private

Split subnet

Divide 192.168.1.0/24 into smaller networks.

  • 1. 192.168.1.0/26

    Hosts: 62

    Range: 192.168.1.1 – 192.168.1.62

  • 2. 192.168.1.64/26

    Hosts: 62

    Range: 192.168.1.65 – 192.168.1.126

  • 3. 192.168.1.128/26

    Hosts: 62

    Range: 192.168.1.129 – 192.168.1.190

  • 4. 192.168.1.192/26

    Hosts: 62

    Range: 192.168.1.193 – 192.168.1.254

Binary view (192.168.1.0/24)

11000000

192

10101000

168

00000001

1

00000000

0

Network bits (24)Host bits (8)

Export & share

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How to use

  1. Enter an address with prefix, such as 192.168.1.0/24, or pick an example.
  2. Review metrics, the range visualization, and network details. Host bits are gray in the binary view.
  3. Split into a longer prefix, then export JSON or CSV. Share the page URL—it includes the CIDR query.

Examples

  • Office VLAN

    Use 10.0.0.0/24 to list usable hosts and broadcast boundaries.

  • Point-to-point

    Use 10.0.0.0/31 for RFC 3021 links (both addresses usable, no broadcast).

  • IPv6 allocation

    Use 2001:db8::/64 to view address counts without IPv4 broadcast rules.

Subnet splitting lists up to 256 child networks per page set. Very large IPv6 counts use BigInt and are shown as decimal strings.

FAQ

What does CIDR notation mean?
The number after the slash is the prefix length: how many leading bits identify the network. /24 on IPv4 is 255.255.255.0; /64 on IPv6 is a typical LAN allocation.
How do subnet masks work?
An IPv4 subnet mask has 1-bits for the network and 0-bits for hosts. The wildcard mask is the inverse. IPv6 uses prefix length only—there is no dotted mask.
Does IPv6 have broadcast or usable-host minus two?
No. IPv6 results omit broadcast and the IPv4 “minus network and broadcast” host count.
How do /30, /31, and /32 behave?
/30 has 2 usable hosts (classic point-to-point). /31 follows RFC 3021: both addresses are usable and there is no broadcast. /32 is a single host route.
How do I split a subnet?
Choose a longer prefix than the parent. A /24 split into /26 yields four equal /26 networks. The new prefix cannot be shorter than the parent.
Where do calculations run?
Entirely in your browser using BigInt-safe arithmetic. Nothing is stored on a server.

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