Subnet Calculator
Find an IPv4 network boundary, final address, block size and conventional usable-host count.
Result for the values shown.
Calculations run in your browser.
What to enter
| Input | Meaning and units |
|---|---|
| IP address | strict IPv4 dotted decimal |
| Prefix length | integer 0..32 |
Understanding your result
The output applies the selected format or address convention. Encoding is not encryption; a valid address representation does not establish availability, reachability or security.
Common mistakes
- Using a different alphabet, padding, base, delimiter or address-prefix convention than the tool expects.
Check your calculation
- Where a reverse operation exists, round-trip a short known example. Compare structural results with the reference example rather than executing decoded text.
Calculation checks, sources and review limits
What network, final address and address count belong to this IPv4 subnet?
Find an IPv4 network boundary, final address, block size and conventional usable-host count.
Common uses
- Find an IPv4 network boundary, final address, block size and conventional usable-host count.
How it works
Split a 32-bit IPv4 address into prefix and host bits. For /0 through /30, the conventional host count excludes network and broadcast addresses. A /31 follows the point-to-point two-address convention in RFC 3021; a /32 is one address. This does not check whether an address is globally routable or available.
Worked example
Enter IP address: 192.168.1.130; Prefix length: 26. The result is Network: 192.168.1.128; Last address: 192.168.1.191; Total addresses: 64; Usable hosts: 62.
FAQ
What network, final address and address count belong to this IPv4 subnet?
Split a 32-bit IPv4 address into prefix and host bits. For /0 through /30, the conventional host count excludes network and broadcast addresses. A /31 follows the point-to-point two-address convention in RFC 3021; a /32 is one address. This does not check whether an address is globally routable or available.
What assumptions and limits apply?
Conventional usable hosts=total-2 for /0../30; /31 uses both addresses only on point-to-point links under RFC3021; /32 single address. Return exceptions explicitly.