Calculators
Open Subnet Calculator →A prefix separates network and host bits
An IPv4 address has 32 bits. A /24 prefix uses 24 of them for the network portion and leaves eight bits, giving 256 total addresses. A dotted mask such as 255.255.255.0 expresses the same prefix. Enter an address with its CIDR length or supported mask in Subnet Calculator. These calculations run locally; they do not send probes to the calculated range.
Read the IPv4 example carefully
For 192.168.10.73/26, the block contains 64 addresses. The network is 192.168.10.64 and the broadcast address is 192.168.10.127. In a conventional multi-access subnet the host range is .65 through .126, or 62 addresses. That number is not automatically the number your platform will let you assign: cloud networks and operational reservations can reduce the available allocation.
Keep edge cases and classification separate
The familiar total-minus-two rule applies to conventional IPv4 subnets, not every prefix. /31 has a defined point-to-point use and /32 identifies a single address. Historical A/B/C classes do not replace an explicit CIDR prefix. Private/public labels are also separate from subnet size; an address outside private space can still be reserved or unsuitable for public routing.
Switch the model for IPv6
IPv6 uses 128-bit addresses and has no broadcast address or A/B/C classes. A prefix describes a block size, not a practical count of automatically usable hosts. For example, 2001:db8::/64 is a documentation prefix with 2^64 addresses. Use Subnet Planner when you need to divide a parent network into multiple allocations, then check overlap, routing and platform requirements before deployment.
Worked example
Illustrative example — not a live test Input: 192.168.10.73/26 Mask: 255.255.255.192 Network: 192.168.10.64 Broadcast: 192.168.10.127 Conventional host range: 192.168.10.65–192.168.10.126
What to check next
- Enter the address and explicit prefix or mask.
- Check network boundaries and prefix-specific host rules.
- Use Subnet Planner for multiple allocations and verify platform reservations.
Common questions
Does a calculated range prove the addresses are reachable?
No. It is address arithmetic. Routing, firewalls and interface configuration are separate.
Should I subtract two addresses from an IPv6 subnet?
No. The conventional IPv4 network/broadcast subtraction does not describe IPv6 addressing.