Subnet Calculator — Free IPv4 Subnet Mask Calculator Online
Free online subnet calculator. Enter any IPv4 CIDR block to instantly get network address, subnet mask, broadcast address, wildcard mask, usable host range, ...
To calculate an IPv4 subnet, type an address in CIDR notation such as 192.168.0.1/24; the subnet mask, network, broadcast, host range and size appear instantly.
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Subnet Calculator — Free IPv4 Subnet Mask Calculator Online. Free online subnet calculator. Enter any IPv4 CIDR block to instantly get network address, subnet mask, broadcast address, wildcard mask, usable host range, and IP class.
Calculate any IPv4 subnet instantly with our free online subnet calculator. Enter any IP address in CIDR notation (e.g.
192.168.0.1/24) to get the network address, subnet mask, broadcast address, wildcard mask, usable host range, total network size, and IP class — all computed in your browser with no data sent to any server.
Perfect for network engineers, CCNA students, cloud architects, and sysadmins configuring VLANs, VPCs, and firewall rules.
Our subnet mask calculator and CIDR calculator supports every IPv4 prefix length from /0 to /32 (or a dotted mask such as 255.255.0.0), correctly handling classful A/B/C subnets and CIDR supernets.
Navigate through adjacent subnet blocks with the Previous / Next block buttons to plan IP address allocations across contiguous ranges.
Use it alongside our IPv4 Range Expander and IPv4 Address Converter for a complete ip subnet calculator and network planning toolkit.
Frequently asked questions
How do I use this subnet calculator?
Type an IPv4 address with its prefix into the field, for example 10.0.5.20/22. The table updates as you type and shows the netmask, network address, network mask (also in binary), CIDR notation, wildcard mask, network size, first and last address, broadcast address and IP class. Click any value to copy it.
Can I enter a subnet mask instead of a CIDR prefix?
Yes. Besides 192.168.0.1/24 you can write the dotted mask after the slash, like 10.0.0.0/255.255.0.0, and the calculator shows it as /16. An address without any mask is treated as a single host (/32). A mask separated by a space is not accepted.
What do the first address and last address show?
They are the first and last usable host addresses of the subnet, so the network and broadcast addresses are excluded. For 192.168.0.1/24 that is 192.168.0.1 to 192.168.0.254, while Network size counts all 256 addresses in the block.
What is a wildcard mask?
The wildcard mask is the inverse of the subnet mask: 255.255.255.0 becomes 0.0.0.255. Cisco access lists and OSPF network statements use it to say which bits of an address may vary.
Why does it say there is no broadcast address?
A /31 or /32 network has no broadcast address. A /32 is a single host and a /31 is a point-to-point link (RFC 3021) where both addresses are usable, so the calculator shows No broadcast address with this mask.
What do the Previous block and Next block buttons do?
They jump to the adjacent subnet of the same size. From 192.168.0.0/24, Next block moves to 192.168.1.0/24 and Previous block to 192.167.255.0/24, which helps when planning contiguous address ranges.
How to use this online tool
Subnet Calculator — Free IPv4 Subnet Mask Calculator Online is designed for fast browser workflows when you need to format, validate, convert, decode, encode, generate, or inspect data without opening a heavy desktop app. Start with the input field or visible options, review the result, then copy or download the output for the next step.
Private processing in your browser
Subnet Calculator — Free IPv4 Subnet Mask Calculator Online keeps the normal processing step local in your browser. That is useful for code snippets, tokens, documents, configuration values, text samples, and other material that should not be sent to a remote service unless you explicitly choose to share it.
When this tool is useful
Use Subnet Calculator — Free IPv4 Subnet Mask Calculator Online for repeatable developer tasks, technical documentation, QA checks, quick conversions, debugging, content cleanup, and internal team workflows. The page focuses on clear inputs, immediate feedback, and output that is easy to reuse in code, reports, tickets, emails, or notes.
Practical tips
Before copying the final result, check important details such as spacing, casing, filenames, encoding, token structure, line breaks, or output format. Small checks prevent mistakes when the result is reused in source code, API requests, documentation, spreadsheets, or shared files.