Calculator

The Calculator tab is the main view of IP Calculator. It displays comprehensive network and mask details for any IPv4 or IPv6 address and prefix combination, along with a binary bit visualisation and subnet enumeration.

Network Details (IPv4)

When an IPv4 address and prefix are entered, the Network Details panel shows:

CIDR

The network address in CIDR notation (e.g. 192.168.1.0/24).

Network

The network address (the first address in the range).

Broadcast

The broadcast address (the last address in the range).

First Host

The first usable host address in the subnet.

Last Host

The last usable host address in the subnet.

Usable Hosts

The number of addresses available for hosts (total minus network and broadcast).

Total

The total number of addresses in the subnet.

Decimal

The network address expressed as a decimal integer.

For /31 prefixes (point-to-point links per RFC 3021), there are no dedicated network or broadcast addresses and both addresses are usable. For /32 prefixes (host routes), the network contains a single address.

Mask Details (IPv4)

Subnet Mask

The subnet mask in dotted-decimal notation (e.g. 255.255.255.0).

Wildcard

The wildcard (inverse) mask, commonly used in ACL configurations.

Hex Mask

The subnet mask in hexadecimal notation.

Mask Bits

The number of bits set to 1 in the subnet mask (equal to the prefix length).

Host Bits

The number of bits available for host addressing.

Scope

The address scope or category (e.g. Private, Public, Loopback, Link-local).

Class

The classful network class (A, B, C, D or E) based on the first octet.

Default Mask

The default subnet mask for the classful network class.

Binary Visualisation

Below the details panels, the Binary Visualisation section displays all 32 address bits as individual cells. Network bits and host bits are colour-coded in different colours, making it easy to see the boundary between the network and host portions of the address. As you change the prefix length, the boundary shifts accordingly.

This visualisation is particularly useful for understanding how subnetting works at the bit level, and is an excellent study aid for networking certification exams.

Input modes

The Calculator supports three input modes. In Hosts needed mode, you enter the number of hosts required and IP Calculator selects the smallest prefix that provides at least that many usable addresses:

In Subnets mode, you specify how many equal subnets you need, and IP Calculator determines the appropriate child prefix length:

IPv6 mode

Switching to IPv6 mode adapts the calculator for 128-bit addresses. The details panels change to show IPv6-specific information:

Address Details (IPv6)

Compressed

The address in compressed notation with leading zeroes and consecutive zero groups omitted.

Expanded

The full 128-bit address with all groups and leading zeroes shown.

Interface ID

The host portion of the address (the bits after the prefix).

Total

The total number of addresses in the prefix.

Prefix Details (IPv6)

Prefix

The network prefix in CIDR notation.

Host Bits

The number of bits available for host addressing.

Scope

The address scope (e.g. Global Unicast, Link-local, Unique Local).

/48 subnets

The number of /48 subnets that fit within this prefix (shown when applicable).

/64 subnets

The number of /64 subnets that fit within this prefix (shown when applicable).

The Binary Visualisation in IPv6 mode displays all 128 address bits, using the same colour-coding for network and host portions.