Subnet Calculator

IP subnetting Calculators. A CIDR Subnet calculator, An IP address range calculator and a subnet mask calculator to cover your subnetting needs in one location.

Subnet Calculator

CIDR subnet calculator, will provide you all needed subnet information given your CIDR notation. Subnet mask, Broadcast Address, Network Address and Usable addresses.

Enter IP/Netmask:

(input format: or

Subnet Calculations:

Usable Addresses:
Mask: =
Mask in HEX:
Network Address:
First Usable:
Last Usable:
Broadcast Address:
Check our subnet cheat sheet for more subnetting practice
CIDR space size to Subnet Mask calculator

Provide the number of addresses required for your subnet below and the calculator will provide you with the correct subnet mask to use.

Enter Number of Addresses Needed:

Subnet Mask Calculations:

Dotted DEC Mask:
Usable Amount of Addresses:
Subnet Mask to CIDR space size

Enter your subnet mask below to get the number of usable host addresses within that subnet and subnet mask in dotted notation.

Enter Mask: /

Address Calculations:

Usable Amount of Addresses:
Total Number of Addresses:
Netmaks in Dotted Decimal Format:

What is a Subnet calculator?

When networks become too large and broadcast domains need to be segmented, the network needs to be broken into smaller parts called subnets or segements. The practice of dividing the network is called subnetting, and a tool that can identify these different divisions is called a subnetting calculator.

Why do I need a subnet calculator?

Subnetting is easy if you are used to it, if you are just starting it might be confusing and time consuming, specially if you are subnetting a large network. A subnet calculator can be used as a practie tool or to prevent human error and make the task easier and faster to do.

How subnetting works?

An IP address is comprised of a network number and a host identifier within that network. A routing prefix is often expressed using Classless Inter-Domain Routing (CIDR) notation for both IPv4 and IPv6. CIDR is a method used to create unique identifiers for networks, as well as individual devices. For IPv4, networks can also be characterized using a subnet mask, which is sometimes expressed in dot-decimal notation, as shown in the "Subnet" field in the calculator. All hosts on a subnetwork have the same network prefix, unlike the host identifier, which is a unique local identification. In IPv4, these subnet masks are used to differentiate the network number and host identifier. In IPv6, the network prefix performs a similar function as the subnet mask in IPv4, with the prefix length representing the number of bits in the address.

What is a CIDR notation?

CIDR notation is a compact representation of an IP address and its associated network mask. CIDR notation specifies an IP address, a slash ('/') character, and a decimal number. The decimal number is the count of consecutive leading 1-bits (from left to right) in the network mask. The number can also be thought of as the width (in bits) of the network prefix. The IP address in CIDR notation is always represented according to the standards for IPv4 or IPv6. The address may denote a specific interface address (including a host identifier, such as, or it may be the beginning address of an entire network (using a host identifier of 0, as in or its equivalent 10/8). CIDR notation can even be used with no IP address at all, e.g. when referring to a /24 as a generic description of an IPv4 network that has a 24-bit prefix and 8-bit host numbers.

What is a subnet mask?

A subnet mask is a bitmask that encodes the prefix length associated with an IPv4 address or network in quad-dotted notation: 32 bits, starting with a number of 1-bits equal to the prefix length, ending with 0-bits, and encoded in four-part dotted-decimal format: A subnet mask encodes the same information as a prefix length but predates the advent of CIDR. In CIDR notation, the prefix bits are always contiguous.