Enter an IP address with CIDR notation to calculate network address, broadcast, subnet mask, host range, and more.
Enter an IPv4 address with CIDR prefix (e.g., 10.0.0.0/8, 172.16.5.10/20)
Subnet Information
About Subnet Calculator Online — Free IPv4 Subnet Tool
This free subnet calculator online is an essential utility for network administrators, IT professionals, system engineers, and students learning TCP/IP networking. Enter any IPv4 address in CIDR notation and instantly receive the network address, broadcast address, subnet mask, wildcard mask, usable host range, total address count, IP class, and whether the address is private or public. All calculations run in your browser with no software to install and no account required.
Subnetting mistakes can bring down entire network segments, cause routing failures, or block hundreds of devices from communicating. Whether you are designing a corporate LAN, configuring a router, studying for a CCNA exam, or segmenting a home lab, having an accurate subnet calculator online at hand eliminates arithmetic errors and speeds up your workflow. The tool also supports binary representation, making it ideal for students who need to see the bit-level breakdown of each address component.
How to Use the Subnet Calculator
Locate the IP Address / CIDR input field at the top of the tool panel.
Type an IPv4 address followed by a forward slash and the prefix length — for example 192.168.1.0/24 or 10.0.0.0/8. The host portion of the address does not need to be zeroed out; the calculator handles any valid IP.
Optionally check Show binary representation if you want to see each address rendered in binary — useful for understanding how the network and host bits are divided.
Click Calculate. Results appear immediately below the input, including network address, broadcast address, subnet mask, wildcard mask, first and last usable host, usable host count, total addresses, CIDR notation, IP class, and address type (private or public).
Use Clear to reset the form for a new calculation. You can run as many calculations as needed without reloading the page.
What the Results Mean
The calculator returns several values for each subnet. Understanding each one helps you correctly configure routers, firewalls, and hosts.
Network Address: The first address in the subnet, where all host bits are zero. This address identifies the subnet itself and cannot be assigned to a device. For 192.168.1.0/24 the network address is 192.168.1.0.
Broadcast Address: The last address in the subnet, where all host bits are one. Packets sent to this address are delivered to every host in the subnet. It cannot be assigned to a device either.
Subnet Mask: A 32-bit value where the network bits are all 1s and the host bits are all 0s. Expressed in dotted-decimal notation, a /24 prefix gives 255.255.255.0. Routers use this mask to determine which part of an IP address is the network portion.
Wildcard Mask: The bitwise inverse of the subnet mask. Used in Cisco ACL and OSPF configurations to define address ranges. A /24 subnet has a wildcard of 0.0.0.255, meaning the last 8 bits can be anything.
Usable Hosts: The count of IP addresses available for assignment to devices. Calculated as 2^(32 minus prefix) minus 2, subtracting the network and broadcast addresses.
Tips for Getting the Best Results
These tips will help you work faster and avoid common subnetting mistakes when using the calculator.
You can enter any host address, not just the network address: If you type 192.168.1.45/24, the calculator correctly identifies the network as 192.168.1.0. You do not need to pre-calculate the network address before using the tool.
Use binary view when studying for exams: Enabling the binary representation option shows each address as eight groups of eight bits. This is the best way to visually confirm which bits belong to the network portion and which to the host portion, which is a core skill tested in CompTIA Network+ and Cisco CCNA exams.
Check the address type for security planning: The tool indicates whether an IP is private (RFC 1918) or public. Private ranges — 10.x.x.x, 172.16–31.x.x, and 192.168.x.x — are not routable on the public internet without NAT. Confirming this prevents configuration errors when setting up internal versus external interfaces.
Use /30 subnets for point-to-point links: A /30 subnet gives exactly 2 usable host addresses, which is the standard for router-to-router links. Use the calculator to quickly verify the host range and broadcast for each link in your network diagram.
Plan address space using a /16 or /8 starting point: Calculate a large parent block first, then work down to smaller subnets by increasing the prefix length. For example, start with 10.0.0.0/8 to understand the full range, then calculate 10.1.0.0/24 for individual segments.
Why Use a Subnet Calculator Online
Manual subnetting requires converting between decimal and binary, applying bitwise AND operations, and recalculating host counts — all error-prone steps that slow down network design work. An online subnet calculator eliminates this entirely. Because it runs in your browser, it is available on any device with internet access, including locked-down work computers where you cannot install software. The calculation is instantaneous, and switching between different prefix lengths takes only seconds.
Network engineers, IT students preparing for certification exams, and home lab enthusiasts all benefit from a reliable subnet calculator that is always one browser tab away. The binary view makes it a learning tool as well as a productivity tool, helping users build intuition for how CIDR subnetting works at the bit level.
Frequently Asked Questions about Subnet Calculator Online
/24 means 24 bits are used for the network portion of the address, leaving 8 bits for hosts. This produces 256 total addresses with subnet mask 255.255.255.0. Two addresses are reserved — the network address and the broadcast address — leaving 254 usable host addresses. The /24 subnet is the most commonly used size for small office and home networks.
The wildcard mask is the bitwise inverse of the subnet mask. Every bit that is 0 in the subnet mask becomes 1 in the wildcard mask, and vice versa. Wildcard masks are used in Cisco router access control lists and OSPF network statements to specify which bits of an address must match exactly and which bits can be anything. For a /24 subnet with mask 255.255.255.0, the wildcard is 0.0.0.255.
In every IPv4 subnet, the first address (all host bits set to zero) is the network identifier address, and the last address (all host bits set to one) is the broadcast address. Neither can be assigned to a host. Both are reserved by the IP protocol specification. So a /24 with 256 total addresses has 254 usable addresses, a /25 with 128 has 126 usable, and so on. The exception is /31 and /32 prefixes used in special configurations.
Currently this calculator supports IPv4 only, covering all prefix lengths from /0 to /32. IPv6 subnetting uses a 128-bit address space and different conventions, and IPv6 support may be added in a future version of the tool. For IPv6 calculations, the same concepts of network prefix and host portion apply, but the numbers involved are significantly larger.
Yes, completely free with no account, subscription, or sign-up required. You can run as many subnet calculations as you need. The tool is ad-supported, which keeps it free for all users. There are no limits on the number of calculations per session or per day.
Yes. All subnet calculations are performed entirely in your browser using client-side JavaScript. The IP address you enter is never sent to any server and is not logged, stored, or transmitted anywhere. Your calculation data stays completely on your own device. This is safe to use with real network addresses from your production environment.
Yes. The subnet calculator is fully responsive and works in mobile browsers on iOS and Android. The IP address input accepts standard text entry, and the results panel is readable on small screens. It is useful on a phone or tablet when you are working on-site and need to quickly verify subnet details without a laptop.
The network address identifies an entire subnet and has all host bits set to zero — it cannot be assigned to a device. A host address is any address within that subnet that has at least one host bit set to a non-zero value, excluding the broadcast address. When you configure a router interface or a server's IP address, you are assigning a host address from within the desired subnet.