Subnet Host Count
Calculator
Results
- Total addresses
- 256
- Usable hosts
- 254
- Host bits remaining
- 8
- Subnets per /24
- 1
Computing results
| Total addresses | 256 |
| Usable hosts | 254 |
| Host bits remaining | 8 |
| Subnets per /24 | 1 |
formula-map diagram
- Total addresses
- 256
- Usable hosts
- 254
- Host bits remaining
- 8
- Subnets per /24
- 1
Computing relationship
Formula
addresses = 2^(32 − prefix) ; usable = addresses − 2= 256
Note
This is a simplified model: it applies the standard computing formula to the numbers you entered and ignores protocol overhead, compression variability, retries, contention and other real-world effects. Size your systems with measured data.
More in Technology and computing
See all →Frequently asked questions
What does this calculator determine?+
It calculates how many usable host addresses are available in an IPv4 subnet based on the subnet mask or prefix length (like /24), by computing the total addresses in that block and subtracting the ones reserved for network and broadcast purposes.
Why do I subtract 2 from the total address count?+
In a standard subnet, the first address is reserved to identify the network itself and the last address is reserved as the broadcast address for that subnet — neither can be assigned to an individual device, so usable hosts equal the total addresses in the block minus 2.
Why does a /31 or /32 subnet behave differently?+
A /31 subnet, used for point-to-point links, has a special exception allowing both addresses to be used as hosts since there's no need for a broadcast address with only two devices. A /32 subnet is a single address with no room for network/broadcast reservations, typically used to identify one specific host or interface.
How does the prefix length relate to the number of hosts?+
Every time you decrease the prefix length by 1 (making the network portion smaller), the number of available host addresses doubles, since you're freeing up one more bit for host addressing. A /24 gives 254 usable hosts, while a /23 gives 510, and a /25 gives only 126.
Why would I use a smaller subnet instead of one large one?+
Subnetting into smaller blocks reduces broadcast traffic, improves network security through isolation, and lets you allocate address space efficiently to match the actual number of devices in each segment, rather than wasting a large block of addresses on a small department or location.