First Host Calculator
Find the first usable host address in an IP subnet.
About First Host Calculator
The first usable host address in a subnet is simply the network address plus one. The network address itself is reserved to identify the subnet, so the next sequential address is the first one assignable to a device.
Formula
First host
first_host = network_address + 1
- network_address
- The subnet's base address (all host bits zero)
Worked example
With the default values below, First Host Calculator returns First Usable Host of 192.168.10.1. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Network Address
- 192.168.10.0
- Prefix Lengthaccepts 0–31
- 24
Results
- First Usable Host
- 192.168.10.1
- Network Address
- 192.168.10.0
- Prefix
- /24
Step by step
- 1Network address= 3232238080
- 2Add 1 for first host= 192.168.10.1
Assumptions and limits
- The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
What about /31 subnets?
RFC 3021 allows both addresses in a /31 subnet to be used as host addresses on point-to-point links, since neither broadcast nor a separate network address is needed between exactly two devices.
Is the first host always the default gateway?
By convention many administrators assign the first (or last) usable address to the default gateway, but this is a convention, not a requirement — the gateway can be any valid host address in the subnet.