Free Online Subnet Calculator
Calculate network address, broadcast, usable hosts, and CIDR ranges.
Accepts a dotted mask such as 255.255.255.0 or a prefix such as /24.
Network details
About the Subnet Calculator
A subnet calculator takes an IPv4 address and a subnet mask and derives the network address, broadcast address, usable host range, and host count. It is a core tool for network engineers, system administrators, and computer-science students studying TCP/IP.
Key terms
- Network address: the first address in the subnet, used to identify the network itself.
- Broadcast address: the last address, used to reach every host in the subnet.
- Subnet mask: a bit pattern that separates the network portion of an address from the host portion.
- CIDR prefix: the number of leading network bits, written as
/24. - Wildcard mask: the inverse of the subnet mask, used in access control lists.
Host counts
A /24 subnet contains 256 addresses. The network and broadcast addresses cannot be assigned to
hosts, leaving 254 usable addresses. A /31 point-to-point link uses two addresses under RFC 3021,
and a /32 represents a single host route.
Frequently asked questions
Why is my IP address not in the host range?
The calculator reports the subnet that contains the address. If the address is the network or broadcast address, it will not appear as a usable host.
Does this support IPv6?
No. This tool is for IPv4 only. IPv6 prefixes use 128 bits and a different notation, so they need a separate calculator.
What is a private IP address?
Private ranges such as 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 are reserved for internal networks and are not routed on the public internet.