IPv4 Subnet Calculator
Enter an IP address and prefix or subnet mask to calculate all network details.
Network
192.168.1.0/24
Broadcast
192.168.1.255
Usable Hosts
254
Class / Type
C / Private
Subnet Details
| IP Address | 192.168.1.100 |
| Network Address | 192.168.1.0 |
| Broadcast Address | 192.168.1.255 |
| First Host | 192.168.1.1 |
| Last Host | 192.168.1.254 |
| Subnet Mask | 255.255.255.0 |
| Wildcard Mask | 0.0.0.255 |
| CIDR Notation | /24 |
| Total Addresses | 256 |
| Usable Hosts | 254 |
| Network Class | C |
| IP Type | Private |
Binary Representation
IP Address
Subnet Mask
How to use the calculator
Enter an address such as 192.168.1.100 and pick a CIDR prefix like /24, or switch to mask mode and type the equivalent, 255.255.255.0. The result updates as you type, with no manual binary conversion.
The tool works out which network the address belongs to and shows the parameters used day to day for planning, configuring and troubleshooting IPv4 networks. Everything is calculated in your browser: no address is sent to any server.
What a subnet is
A subnet is the logical division of a larger IP network into smaller ones. Dividing lets you organize devices, separate environments, create VLANs, apply security policies and use address space more efficiently.
In 192.168.1.0/24, the /24 says how many bits of the address identify the network. That prefix matches the mask 255.255.255.0 and marks out a block of 256 addresses.
What CIDR means
CIDR stands for Classless Inter-Domain Routing and is the usual way to express the size of a network. In 192.168.1.0/24, the 24-bit prefix identifies the network and the remaining 8 bits identify hosts within it.
The larger the number after the slash, the smaller the block. The prefixes /24, /26, /27 and /30 describe progressively smaller networks, holding 256, 64, 32 and 4 addresses.
What the calculator reports
From the address and the prefix or mask, the tool shows:
- Network address and broadcast address
- First and last address usable by a host
- Subnet mask and wildcard mask
- Total addresses and usable host count
- Address class, and whether it falls in a private or public range
- Binary view of the address and the mask, with the network bits highlighted
Example: a /24 network
Take 192.168.1.100/24. The address belongs to 192.168.1.0/24, where 192.168.1.0 identifies the network and 192.168.1.255 is the broadcast address. Addresses from 192.168.1.1 to 192.168.1.254 are available to hosts, 254 in total.
The gap between 256 and 254 is exactly the network and broadcast addresses, neither of which can be assigned to equipment.
About classes A, B and C
The calculator reports the address class because the term still turns up in documentation and certification exams. In practice classful addressing was replaced by CIDR back in the 1990s: what defines the size of a network today is the prefix, not the first octet.
Treat the class as historical context and make decisions from the prefix.
What a subnet calculator is for
It is used to size networks, check interface configuration, define VLANs, validate firewall rules, plan DHCP ranges and quickly confirm whether two addresses sit in the same network.
It is also a practical study aid for subnetting, TCP/IP and infrastructure certifications, because it shows the answer next to the binary view that explains how it was reached.
Frequently asked questions
What does /24 mean?
It means the first 24 bits of the address identify the network and the remaining 8 identify hosts. The /24 prefix is equivalent to the mask 255.255.255.0.
How many hosts are in a /24 network?
A /24 holds 256 addresses, of which 254 are available to hosts. The two left over are the network address and the broadcast address.
How many hosts are in /30, /31 and /32?
A /30 holds 4 addresses and 2 usable hosts, the classic shape for a point-to-point link. A /31 holds just 2 addresses and both can be used on the link, as described in RFC 3021, because no broadcast is needed there. A /32 identifies a single address and is used for host routes, loopback interfaces and firewall rules.
What is the difference between CIDR and a subnet mask?
They are two notations for the same thing. The /24 prefix and the mask 255.255.255.0 describe exactly the same split between network bits and host bits. The calculator accepts either form.
What is the broadcast address?
It is the last address in the block, used to send traffic to every device on that subnet at once. That is why it cannot be assigned to a piece of equipment.
What is a wildcard mask?
It is the bitwise inverse of the subnet mask: where the mask has a 1, the wildcard has a 0. It appears in Cisco access control lists and in the configuration of routing protocols such as OSPF.
What are private IP addresses?
They are ranges reserved by RFC 1918 for internal networks and not routed on the public internet: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. The calculator flags when the address you entered falls in one of them.
Want to know which address your connection uses to reach the internet? Find out what your IP is
Need to investigate a public address and see which network it belongs to? Look up IP geolocation