IP Subnet Calculator
A precision tool for network engineering and IP address management.
IP Subnet Calculator
Subnetting is one of the most essential skills in networking. Whether you're setting up a small home network or planning a corporate infrastructure, this IP subnet calculator gives you all the details you need — network address, broadcast address, usable host range, and more.
What Does This Calculator Do?
Enter an IP address and either a CIDR prefix length (e.g., /24) or a subnet mask (e.g., 255.255.255.0), and the calculator returns the full subnet information: network address, broadcast address, first and last usable hosts, and total host count.
How to Use This Calculator
- Enter the IP address (e.g., 192.168.1.50).
- Enter the CIDR prefix (e.g., /24) or subnet mask (e.g., 255.255.255.0).
- Click Calculate to see all subnet details.
Key Subnet Concepts
- Network Address: First address in the subnet — identifies the network itself.
- Broadcast Address: Last address — used to send data to all hosts in the subnet.
- Usable Hosts: All addresses between network and broadcast — these are assignable to devices.
- CIDR Notation: /24 means 24 bits are the network portion, leaving 8 bits for hosts (2⁸ − 2 = 254 usable hosts).
Example Calculation
IP: 192.168.10.100/24
- Subnet Mask: 255.255.255.0
- Network Address: 192.168.10.0
- Broadcast Address: 192.168.10.255
- Usable Host Range: 192.168.10.1 – 192.168.10.254
- Total Usable Hosts: 254
Common CIDR Ranges
- /30 = 2 usable hosts (point-to-point links)
- /29 = 6 usable hosts
- /28 = 14 usable hosts
- /27 = 30 usable hosts
- /24 = 254 usable hosts (typical LAN)
- /16 = 65,534 usable hosts
- /8 = 16,777,214 usable hosts
Common Mistakes to Avoid
- Assigning the network or broadcast address to a device — the first and last addresses in any subnet are reserved. Never assign them to hosts.
- Confusing CIDR and subnet mask notation — /24 and 255.255.255.0 are the same thing, just written differently.
- Overlapping subnets in routing — plan your IP addressing scheme carefully to avoid route ambiguity.
Frequently Asked Questions
What is a /24 subnet?
A /24 subnet uses 24 bits for the network and 8 bits for hosts. It supports 256 addresses total, with 254 usable for devices. It's the most common subnet for home and small office networks.
How many subnets can I get from a /24?
Subdividing a /24 into /25 gives you 2 subnets of 126 hosts each. Into /26 gives 4 subnets of 62 hosts. Into /27 gives 8 subnets of 30 hosts each.
What is the difference between IPv4 and IPv6 subnetting?
IPv4 addresses are 32 bits (e.g., 192.168.1.1). IPv6 addresses are 128 bits (e.g., 2001:db8::1). This calculator focuses on IPv4 subnetting.
What is a private IP address range?
RFC 1918 defines three private ranges: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. These are used in internal networks and are not routed on the public internet.
What is the loopback address?
127.0.0.1 (loopback) refers to the local machine itself. It's used for testing and is never routable on a network.
Conclusion
Subnetting is a critical networking skill, and this calculator takes the binary math off your plate. Whether you're studying for a networking certification or planning a real deployment, it gives you accurate subnet information in seconds.
Related: Bandwidth Calculator | Conversion Calculator
Subnetting Tip
Did you know? Subnetting a /24 into two /25s gives you 126 usable hosts per network instead of 254 in a single /24, but it improves security and isolates broadcast storms.
