Skip to main content
IP Range CalculatorPRO
IPv4 Subnetting & RangeInstant Client-Side Tool

First and Last Address Calculator

Identify a range’s endpoints.

First and Last Address Calculator: inputs and results

Enter an IP address, CIDR prefix, or range. Then check its first and last address below.

Quick presets:

Calculated Boundaries & ParametersReady

Network Address192.168.1.0
Broadcast Address192.168.1.255
First Usable Host192.168.1.1
Last Usable Host192.168.1.254
Subnet Mask255.255.255.0
Wildcard Mask0.0.0.255
Total Addresses256
Usable Host Range254

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.
Open Full Interactive Suite

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.

Usable IPv4 Host Range Calculator

Apply the selected subnet-use rules.

Total Address Count Calculator

Count addresses within a prefix.

How First and Last Address Calculator Works?

This tool works by returning the lowest and highest address of a CIDR block, with no addresses removed for network or broadcast use.

  1. Enter a CIDR block

    Type a block such as 100.64.0.0/10 or any address with a prefix.

  2. Round down to the block start

    The calculator aligns the address to the prefix boundary. The aligned value is the first address.

  3. Add the block size

    The last address equals the first address plus 2^(32−p) − 1.

  4. Show both endpoints

    The calculator prints both endpoints side by side, ready for range-based tools and spreadsheets.

First and Last Address Calculator Formula

The formula is First = IP AND Mask, and Last = First + 2^(32 − p) − 1.

First address

First = IP AND Mask

The block start, with every host bit at 0.

Last address

Last = First + 2^(32−p) − 1

The block end, with every host bit at 1.

Span check

Last − First + 1 = 2^(32−p)

The endpoints always enclose an exact multiple of 2 addresses (except /32).

Worked example: 100.64.0.0/10 (shared address space, RFC 6598)

Host bits = 32 − 10 = 22
Size      = 2^22 = 4,194,304 addresses
First     = 100.64.0.0
Last      = 100.64.0.0 + 4,194,303 = 100.127.255.255

First and Last Address Calculator Conversion Table

The table lists the first address, last address, and size of 10 well-known and sample IPv4 blocks.

CIDR BlockFirst AddressLast AddressSize
10.0.0.0/810.0.0.010.255.255.25516,777,216
172.16.0.0/12172.16.0.0172.31.255.2551,048,576
192.168.0.0/16192.168.0.0192.168.255.25565,536
100.64.0.0/10100.64.0.0100.127.255.2554,194,304
169.254.0.0/16169.254.0.0169.254.255.25565,536
198.18.0.0/15198.18.0.0198.19.255.255131,072
192.0.2.0/24192.0.2.0192.0.2.255256
10.10.10.64/2610.10.10.6410.10.10.12764
10.10.10.128/2510.10.10.12810.10.10.255128
172.31.255.240/28172.31.255.240172.31.255.25516

What is First and Last Address Calculator?

The First and Last Address Calculator is a tool that identifies the 2 endpoints of an IPv4 address block: the lowest address and the highest address. The tool reports the full span of the block, not the usable host range.

Endpoints matter whenever a system stores address space as intervals. Databases, geolocation feeds, and many firewall vendors use a start–end pair. The First and Last Address Calculator converts CIDR notation into that pair without applying host reservation rules.

For a /24 such as 192.0.2.0/24, the first address is 192.0.2.0 and the last is 192.0.2.255. The usable host range (.1 to .254) is a separate calculation.

What are the uses of First and Last Address Calculator?

There are 5 main uses of the First and Last Address Calculator, including database range storage, registry lookups, and documentation.

  • Storing ranges in databases

    SQL tables often store ip_start and ip_end columns. The endpoints convert a prefix into those 2 columns.

  • Matching registry records

    WHOIS and RIR records show allocations as start–end ranges. The endpoints confirm that a prefix matches a record.

  • Reserving special-purpose space

    Teams blocking 100.64.0.0/10 or 198.18.0.0/15 need the full span, including the network and broadcast positions.

  • Building range-based reports

    Spreadsheet reports sort and compare ranges more easily with numeric endpoints.

  • Documenting address plans

    Address plans list each block with its first and last address so readers see the span at a glance.