- Netmask
- Full range
- Usable range
- Total addresses
- Usable addresses
- Complete /64 networks
IPv4 and IPv6 subnet calculator
IPv4 & IPv6 CIDR calculator and subnet planner
Turn an IPv4 or IPv6 address and prefix into its exact range, then divide it into equal child allocations or join valid siblings back together. IPv6 uses exact 128-bit arithmetic without inventing a broadcast address or IPv4-style usable-host count.
Runs locally. No address leaves your browser.
Calculate an IPv4 subnet
Parent range
IPv6 calculated boundaries
- Canonical network prefix
- Fully expanded input
- Fully expanded network
- First address
- Last address
- Address count
- Complete /64 networks
- Prefix bits
- Remaining bits
128-bit boundary
Prefix:Remaining/interface space:
Labels and bit counts identify both sides of the boundary without relying on colour.
Visual subnetting
Parent
Up to 256 current subnets. Branches follow each split, ordered from the network address to the upper boundary.
Choose Split or Join, then activate a current subnet in the visual. Either member of a joinable sibling pair can be used to join it.
Calculated range and binary details
- Network address
- Broadcast address
- First usable
- Last usable
- Netmask
- Wildcard mask
- Total addresses
- Usable addresses
Binary boundary
At high zoom, scroll this panel horizontally to see all 32 bits.
Input
Network
Netmask
Broadcast
Network bitsHost bits
Method
Mask the host bits
The prefix keeps the leading network bits. Setting remaining bits to zero gives the network; setting them to one gives the upper boundary.
IPv4-only edge cases
/31 and /32
A point-to-point /31 can use both addresses under RFC 3021. A /32 identifies one host route, not a multi-address subnet.
IPv6-only edge cases
/127 and /128
A point-to-point /127 can use both addresses under RFC 6164, without an IPv4-style network/broadcast pair. A /128 identifies one address; IPv6 has no broadcast address.
Scope
Two families, honest semantics
IPv6 output uses canonical RFC 5952 text and exact 128-bit ranges. It does not show IPv4-only broadcast, wildcard-mask or usable-host concepts. VLSM-by-host-count and cloud reservations remain outside this calculator.