IPv4 Subnet Calculator

A free online network calculator with a visual subnetting sheet

IP4 Calculator

Advanced Options Classful

Adjacent Networks

This online IPv4 Calculator can be used to calculate subnet information based on an IP address and a subnet mask.

You can fill in an IP address and choose a subnet mask (by using the pulldown on the subnet mask field, or if you prefer the pulldown on the mask bit).

When you know how many hosts you need within a subnet, you can also choose to enter this number at "hosts per subnet". This will result in an IP subnet with the correct number of available IP addresses.

After you have found the right subnet, you can use the subnetting sheet below to divide it further into smaller segments.

Subnetting sheet

Subnetting is the process of dividing a network into smaller networks, known as subnetworks or subnets.

The primary considerations in designing IP networks are determining the number of required subnets and the number of hosts needed in each subnet.

After calculating the supernet (using the IP calculator), we can further divide it with this subnetting sheet. By using the "Split" link in the sheet below, we can determine the number of available hosts in the newly created subnets. Keep in mind that we need one IP address for the gateway, so the smallest IP subnet we can create is a /30 subnet. This allocation allows for one IP address for a host and one IP address for the gateway.

Subnet Subnet Mask Mask Assignable Range Hosts Split Join

If you would like to keep this table for future reference, you can save, share, or bookmark URL. Additionally, you have the option to download the sheet as a comma-separated values (CSV) file. This downloaded file can be useful for your documentation purposes; you can add columns for subnet descriptions or corresponding VLAN IDs.

Subnet Cheat Sheet

This serves as a quick reference for IPv4 Subnetting and Subnet masks.

IPv4 Subnet Chart

CIDR Subnet Mask Total IPs Assignable IPs

* /31 subnets are descriped in RFC3021, which was primarily motivated by the potential for public address space conservation. There is no need for a broadcast address in a 'IPv4 Point-to-Point Links'.


IPv4 Classfull Ranges RFC790

Subnet Range Class - A - B - C - D - E


IPv4 Private IP Ranges RFC1918

Subnet Classful description


IPv4 Special-Purpose Ranges RFC5736, RFC6890 & RFC8190

Subnet Description

The private IP addresses actually also belong to this table, but are omitted here because we have listed them in the separate table above.


IP Address: A unique identifier for a device on a network, whether local or internet-based

Subnet Mask: A subnet mask divides an IP address into a host and network address

Network ID: The first IP address in a subnet. This address is utilized for routing purposes and cannot be assigned to a host

Broadcast Address: The last IP address in a subnet. This address is used to send data to all hosts within a subnet and cannot be assigned to a host

Wildcard: The inverse of a netmask. Used by certain firewalls for access control lists

Supernet: Multiple subnets combined into one larger subnet

Gateway: The IP address of the device that connects this subnet to other networks