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 subnet calculator
See exactly what your CIDR contains.
Turn an IPv4 address and prefix into its network range, usable hosts, masks and binary boundary. Clear handling for /31 links and /32 host routes included.
Runs locally. No address leaves your browser.
Calculate an IPv4 subnet
Calculated range
192.168.1.42/24
- Network address
- 192.168.1.0
- Broadcast address
- 192.168.1.255
- First usable
- 192.168.1.1
- Last usable
- 192.168.1.254
- Netmask
- 255.255.255.0
- Wildcard mask
- 0.0.0.255
- Total addresses
- 256
- Usable addresses
- 254
The network and broadcast addresses are reserved in a traditional IPv4 subnet.
Binary boundary
At high zoom, scroll this panel horizontally to see all 32 bits.
Input
Network
Netmask
Broadcast
Network bitsHost bits
Edge cases
/31 and /32
A point-to-point /31 can use both addresses under RFC 3021. A /32identifies one host route, not a multi-address subnet.
Scope
Deliberately IPv4
This first release does not pretend to support IPv6, VLSM or cloud reservations. Those need separate, tested workflows rather than cosmetic switches.