IPv4 Subnet Calculator
Calculate subnet, hosts, CIDR and binary details
Paste an IPv4/CIDR value and inspect network, broadcast, and usable hosts first; scenario presets are available in Advanced mode.
The full guide also includes pitfalls, worked examples, snippets, FAQs, and related tools for checking results or troubleshooting.
About this tool
Calculate IPv4 block boundaries from address/prefix or address plus a contiguous dotted mask. Results include the network, range end, wildcard mask, binary representation and conventional host arithmetic, including /31 and /32. This is a local calculation, not an address-allocation or reachability check.
Production Snippets
An address inside a /27 block
text
192.168.1.33/27
Network: 192.168.1.32
Broadcast: 192.168.1.63
Hosts: 192.168.1.33β192.168.1.62 (30)
Mask: 255.255.255.224Frequently Asked Questions
Which input formats work?
Use 192.168.1.33/27 or 192.168.1.33 255.255.255.224. Prefixes range from /0 to /32. A dotted mask must consist of contiguous one bits followed by zero bits.
Why does a /24 show 254 usable hosts?
It contains 256 addresses. Conventional broadcast-subnet arithmetic excludes the network and directed broadcast addresses, leaving 254; a cloud platform may reserve additional addresses.
What changes for /31 and /32?
A /31 can represent two point-to-point endpoint addresses under RFC 3021. A /32 is one host route. Neither has a separate subnet broadcast address here, so the upper bound is labelled range end.
Are all calculated hosts assignable?
No. Counts do not account for special-use ranges, platform reservations, current leases or routing policy. IP class is historical context and does not determine the CIDR prefix you entered.
Is my network input retained?
Calculation runs locally without probing the IPs. The page saves its input and options as a browser draft; Clear removes the saved input, and site-data controls can remove local storage.
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