Usable IPv4 Host Range Calculator
Apply the selected subnet-use rules.
Usable IPv4 Host Range Calculator: inputs and results
Enter an IP address, CIDR prefix, or range. Then check its first and last address below.
Calculated Boundaries & ParametersReady
Key Capabilities
- •100% Client-Side: Zero telemetry or server latency.
- •RFC Compliant: Exact 32-bit and 128-bit integer precision.
- •Quick Copy: Instant access to CIDR, mask, and range bounds.
- •Cross-Platform: Works on desktop, tablet, and mobile browsers.
Related IPv4 Subnetting & RangeAll Tools
IPv4 Range Calculator
Find address boundaries from a prefix.
IPv4 Subnet Calculator
Calculate subnet details from address and mask.
Network Address Calculator
Find the subnet’s network address.
IPv4 Broadcast Address Calculator
Find broadcast addresses where applicable.
First and Last Address Calculator
Identify a range’s endpoints.
Total Address Count Calculator
Count addresses within a prefix.
How Usable IPv4 Host Range Calculator Works?
This tool works by removing the network address and broadcast address from a subnet and returning the remaining host addresses, with RFC 3021 rules for /31 and host-route rules for /32.
Enter a subnet
Type a prefix such as
198.51.100.0/23.Select the rule set
Prefixes /0 to /30 use the standard rule. A /31 uses the point-to-point rule, and a /32 uses the single-host rule.
Trim the reserved addresses
The standard rule drops 1 address at each end. The first usable host is network + 1 and the last usable host is broadcast − 1.
Report the host range
The calculator prints the host range and the usable count, for example 510 hosts for a /23.
Usable IPv4 Host Range Calculator Formula
The formula is First Host = Network + 1 and Last Host = Broadcast − 1 for prefixes /0 to /30.
Standard rule (/0–/30)
Hosts = [Network + 1, Broadcast − 1]Removes 2 addresses per subnet.
Point-to-point rule (/31)
Hosts = [Network, Network + 1]RFC 3021 makes both addresses usable.
Host route rule (/32)
Hosts = [IP]The single address is the host.
Usable count
Usable = 2^(32−p) − 2Applies to /0 through /30.
Worked example: 198.51.100.0/23
Network = 198.51.100.0 Broadcast = 198.51.101.255 First host = 198.51.100.1 Last host = 198.51.101.254 Usable = 2^9 − 2 = 510 hosts
Usable IPv4 Host Range Calculator Conversion Table
The table shows the usable host range of 198.51.100.0 at 11 prefix lengths, from /22 to /32, with the rule applied to each row.
| Prefix | First Usable Host | Last Usable Host | Usable Hosts | Rule |
|---|---|---|---|---|
| /22 | 198.51.100.1 | 198.51.103.254 | 1,022 | Total − 2 |
| /23 | 198.51.100.1 | 198.51.101.254 | 510 | Total − 2 |
| /24 | 198.51.100.1 | 198.51.100.254 | 254 | Total − 2 |
| /25 | 198.51.100.1 | 198.51.100.126 | 126 | Total − 2 |
| /26 | 198.51.100.1 | 198.51.100.62 | 62 | Total − 2 |
| /27 | 198.51.100.1 | 198.51.100.30 | 30 | Total − 2 |
| /28 | 198.51.100.1 | 198.51.100.14 | 14 | Total − 2 |
| /29 | 198.51.100.1 | 198.51.100.6 | 6 | Total − 2 |
| /30 | 198.51.100.1 | 198.51.100.2 | 2 | Total − 2 |
| /31 | 198.51.100.0 | 198.51.100.1 | 2 | RFC 3021 |
| /32 | 198.51.100.0 | 198.51.100.0 | 1 | Host route |
What is Usable IPv4 Host Range Calculator?
The Usable IPv4 Host Range Calculator is a tool that returns the addresses in an IPv4 subnet that can be assigned to devices. The tool excludes the network address and the broadcast address, which identify the subnet and reach all hosts.
RFC 950 and RFC 1812 reserve the all-zeros and all-ones host values in each subnet. RFC 3021 removes that reservation for /31 point-to-point links, and a /32 prefix describes one host. The Usable IPv4 Host Range Calculator applies the matching rule to each prefix length automatically.
The usable range defines where servers, printers, gateways, and DHCP pools may sit. A /24 such as 192.168.10.0/24 provides 254 usable addresses from .1 to .254.
What are the uses of Usable IPv4 Host Range Calculator?
There are 5 main uses of the Usable IPv4 Host Range Calculator, including static IP assignment, DHCP pool limits, and gateway placement.
Assigning static addresses
Administrators pick server and printer addresses only from the usable range, which prevents conflicts with the network and broadcast addresses.
Setting DHCP pool boundaries
DHCP start and end addresses must fall inside the usable range. The calculator gives the outer limits of the pool.
Placing the default gateway
Most designs put the gateway on the first usable host (
.1) or the last usable host (.254on a /24).Planning point-to-point links
Router-to-router links on /31 prefixes use both addresses. The calculator confirms the 2 usable endpoints.
Validating device configurations
Configuration audits flag hosts that use a network or broadcast address. The usable range is the reference for those checks.