Formula and assumptions
2^(32−CIDR)/31 models point-to-point links; /32 a single host. Real network configuration is not checked.
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IPv4 and CIDR
/31 models point-to-point links; /32 a single host. Real network configuration is not checked.
How many hosts fit in a /24 subnet?
An IPv4 /24 contains 256 addresses and normally supports 254 hosts, reserving network and broadcast addresses. For 192.168.1.42/24, the network is 192.168.1.0.
Calculation assumptions
/31 models point-to-point links; /32 a single host. Real network configuration is not checked.
Result
Fields contain editable examples.
How to use this calculator
Enter an IPv4 address and prefix to find subnet boundaries. A larger prefix leaves fewer address bits and creates a smaller block. The tool does not test routing, DHCP, firewalls or connectivity.
Worked example
- For 192.168.1.42/24, 32 − 24 = 8 bits remain for addresses.
- The block has 2⁸ = 256 addresses: 192.168.1.0 through 192.168.1.255.
- A conventional subnet reserves network and broadcast: 256 − 2 = 254 hosts.
Example result
- Network
- 192.168.1.0
- Mask
- 255.255.255.0
- Broadcast
- 192.168.1.255
- Hosts
- 254
Interpreting the result
For DHCP planning, also exclude your gateway, static assignments and reservations. Calculated hosts do not mean addresses currently free on your network.
Frequently asked questions
How is /31 handled?
As a point-to-point special case with two endpoints and no separate network or broadcast reservation. Check device support.
What does /32 represent?
One individual address, not a conventional multi-host subnet.
What is a wildcard?
The complement of the mask: 0.0.0.255 for /24. Access-list usage depends on device syntax.