How to read an IPv4 subnet result
Calculate a subnet
Enter an address such as 192.168.100.97/27. The address may be any host in the block; it does not have to be the network address.
Select Calculate subnet. The first result is the normalized network address. Copy the complete summary when checking documentation or a configuration.
What the fields mean
The subnet mask has the first prefix bits set to one. The network is the first address in the block and the address range runs from that value through the last address.
For /0 through /30, the final address is the directed broadcast and the ordinary usable host range excludes both endpoints. Total addresses includes every address, while usable hosts applies the displayed prefix semantics.
Boundary examples
192.168.100.97/27 belongs to 192.168.100.96/27, has mask 255.255.255.224, broadcast 192.168.100.127 and 30 traditional usable hosts.
255.255.255.255/0 spans 0.0.0.0 through 255.255.255.255. A /31 has two point-to-point addresses and a /32 identifies one host route.
Scope and safety
Calculations use unsigned arithmetic across the full IPv4 range. Inputs with missing octets, extra text, prefixes above 32 or ambiguous leading-zero octets are rejected.
This tool does not scan networks, contact an address, change router settings, allocate subnets, calculate IPv6 or prove that a proposed block is available.
IPv4 subnet FAQ
Why is /31 shown with two usable hosts?
RFC 3021 permits both addresses on a point-to-point link, so there is no separate network or broadcast endpoint for host counting.
Why does /32 have one usable address?
A /32 is a single-address host route. Its network and host address are the same.
Does the entered IP need to be the network address?
No. Any address in the block is accepted and normalized to its network.
Are private and public ranges treated differently?
No. The arithmetic is identical; this page does not judge routing or ownership.