Subnet Calculator
Quickly calculate IP addresses, subnet masks, and host ranges for your network configuration.
Calculation Settings
Summary Results
Subnet Division
Fast Calculation
Instantly calculate all CIDR values from /16 to /32. View network, broadcast and usable IP ranges.
Subnet Division
Divide large networks into smaller subnets. View detailed information for each subnet in table format.
Easy Copy
Copy calculated values to clipboard with a single click. Use them quickly in your network configuration.
What are CIDR and subnets?
CIDR (Classless Inter-Domain Routing) notation writes an IP block as an address plus a prefix length. In 192.168.1.0/24, the first 24 bits identify the network and the remaining 8 bits the devices (hosts). The larger the prefix, the smaller the block: a /24 has 256 addresses, a /30 has 4.
The calculator shows the network and broadcast addresses, subnet mask, wildcard mask, usable IP range and number of addresses. You can split a block into smaller subnets and see them all in a table. Calculations run in your browser.
How to use
- 1Enter an IPv4 address and choose a prefix between /16 and /32.
- 2Results are calculated as you type; copy any value with its copy button.
- 3To split the block, choose a smaller prefix in the subnet division section.
Frequently asked questions
How many usable IP addresses are in a /24?
A /24 contains 256 addresses. The first is reserved as the network address and the last as the broadcast address, leaving 254 for devices. As a rule, the number of usable addresses is 2 to the power of (32 − prefix), minus 2.
What is the difference between a subnet mask and a wildcard mask?
A subnet mask (for example 255.255.255.0) shows which part of the address belongs to the network. A wildcard mask (0.0.0.255) is its inverse and is used in Cisco access lists (ACLs) and OSPF configurations.
What are /31 and /32 blocks used for?
A /32 is a single IP address, used in firewall rules and for loopback addresses. A /31 is a two-address block; under RFC 3021 both addresses can be used on point-to-point links between two routers.
Which IP ranges are private?
Under RFC 1918, 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 are private ranges used in local networks and are not routed on the internet. Home and office networks usually use 192.168.0.0/24 or 192.168.1.0/24.
Does the calculator support IPv6?
No, it currently works with IPv4 addresses only.