Calculator
CIDR Calculator — IPv4 & IPv6 Subnets, Masks & Hosts
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Version 1.0.0 · Last reviewed
How it worksShow guide
Introduction
Enter an address or CIDR to derive the network, mask, wildcard, first and last host, and usable count. IPv6 returns compressed and expanded forms with no broadcast. Classful A/B/C labels are historical notes only — the prefix is authoritative.
Step-by-step
- Paste an IPv4 or IPv6 address, optionally with /prefix
- Read network, range, and binary fields
- For IPv4, choose a longer prefix to list child subnets
Worked example
Network 192.168.1.0, broadcast 192.168.1.255, usable 254 hosts. Splitting to /26 lists four blocks starting at .0, .64, .128, and .192.
Use cases
- Plan a /24 split into /26s
- Check a /31 point-to-point (RFC 3021)
- Expand a compressed IPv6 prefix
Frequently asked questions
Does this look up WHOIS or geolocation?
No. It only does address arithmetic in your browser.
What about /31 and /32?
A /32 is a single host. A /31 uses both addresses on a point-to-point link (RFC 3021) — there is no unused network/broadcast pair.
Why is there no IPv6 broadcast?
IPv6 does not use broadcast. This calculator shows the first and last addresses in the prefix instead.
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