Subnet calculator

The Subnet Calculator is a comprehensive networking tool that computes all essential information about IP networks for both IPv4 and IPv6 protocols. Enter an IP address with subnet mask or prefix length and instantly get network address, broadcast address, usable host range, binary representations, and generate subnet lists. Essential for network planning, troubleshooting, and IT administration.

The Subnet Calculator interface is organized into several key areas. Understanding each component helps you use the tool efficiently.

1

Protocol tabs (IPv4 / IPv6)

At the top of the calculator, you'll see two tabs - IPv4 and IPv6. Click on a tab to switch between Internet Protocol version 4 (32-bit addresses) and version 6 (128-bit addresses). The entire interface adapts to the selected protocol.

2

Stats bar

Below the protocol tabs is a horizontal bar showing key statistics:
• NETWORK ADDRESS
• BROADCAST (IPv4 only)
• TOTAL HOSTS
• USABLE HOSTS
• SUBNETS

These update in real-time as you enter or modify your input.

3

Class buttons (IPv4 only)

Three buttons labeled A, B, and C let you quickly load example configurations for common network classes. Click a button to auto-fill IP address, subnet mask, and CIDR prefix with typical values for that class.

4

Action buttons row

Four buttons in the upper right:
• Copy: copy results
• History: view previous calculations
• Download: export results
• Delete: clear current input

5

Input area

The main input section contains fields for IP address and subnet mask/prefix. IPv4 shows IPV4 ADDRESS and SUBNET MASK with CIDR dropdown. IPv6 shows IPV6 ADDRESS and PREFIX LENGTH dropdown.

6

Settings bar

Below the inputs:
• Auto-calculate checkbox: enables real-time calculation
• CALCULATE SUBNET button: manual calculation
• CALCULATIONS counter: showing how many calculations you've performed

7

Result tabs

Three tabs display results in different formats:
• Overview: summary cards
• Binary view: binary representations
• Subnet list: generate multiple subnets

Each provides unique insights into your network.

8

Favorites tab

On the right edge of the screen, you'll find the Favorites tab (heart icon). Click it to add this tool to your favorites for quick access from the homepage.

Complete interface with protocol tabs, input fields, result tabs, and favorites

IPv4 (Internet Protocol version 4) uses 32-bit addresses written as four decimal numbers. This is the most common protocol for local and internet networks.

1

Select IPv4 tab

Click the IPv4 tab at the top of the calculator. The interface displays IPv4-specific input fields and the class selection buttons (A, B, C) become visible.

2

Enter IPv4 address

In the IPV4 ADDRESS field, type your IP address in dotted decimal format.
• Format: 192.168.1.100
• Four octets separated by dots
• Each octet ranges from 0 to 255
• Example: 10.0.0.1, 172.16.50.25, 192.168.0.1

3

Enter subnet mask

In the SUBNET MASK field, enter the subnet mask in dotted decimal format.
• Format: 255.255.255.0
• Common masks: 255.0.0.0, 255.255.0.0, 255.255.255.0
• The mask determines which bits are network vs. host

4

Select CIDR prefix (alternative)

Instead of typing the mask, use the CIDR dropdown to select a prefix length.
• Click the dropdown showing /24 (or current value)
• Select from /1 to /32
• Common values: /8 (Class A), /16 (Class B), /24 (Class C)
• The subnet mask field updates automatically

5

Use class buttons (quick selection)

Click A, B, or C button to preset common configurations:
• A: Sets CIDR range /8 to /15 (large networks)
• B: Sets CIDR range /16 to /23 (medium networks)
• C: Sets CIDR range /24 to /32 (small networks)
• The CIDR dropdown options filter to that class

6

Calculate

If Auto-calculate is checked, results appear instantly. Otherwise, click the orange CALCULATE SUBNET button. The stats bar updates with: NETWORK ADDRESS, BROADCAST, TOTAL HOSTS, USABLE HOSTS, and SUBNETS count.

IPv4 mode with input fields and calculation results

7

View results

Results appear in the three tabs below:
• Overview: Summary cards with all key values
• Binary view: Binary representation of addresses
• Subnet list: Generate list of available subnets

Standard LAN:        192.168.1.100 / 255.255.255.0  (/24)
Large enterprise:    10.0.0.1 / 255.0.0.0          (/8)
Medium network:      172.16.50.25 / 255.255.0.0    (/16)
Small segment:       192.168.10.1 / 255.255.255.192 (/26)
Point-to-point:      10.1.1.1 / 255.255.255.252    (/30)

IPv6 (Internet Protocol version 6) uses 128-bit addresses written in hexadecimal. It provides a vastly larger address space than IPv4 and is becoming the standard for modern networks.

1

Select IPv6 tab

Click the IPv6 tab at the top of the calculator. The interface changes to show IPv6-specific fields. Note that class buttons (A, B, C) disappear as IPv6 doesn't use classful addressing.

2

Enter IPv6 address

In the IPV6 ADDRESS field, type your IPv6 address in hexadecimal format.
• Format: 2001:0db8:85a3:0000:0000:8a2e:0370:7334
• Eight groups of four hex digits, separated by colons
• Leading zeros can be omitted: 2001:db8:85a3::8a2e:370:7334
• Consecutive zero groups can be replaced with ::

3

Select prefix length

Use the PREFIX LENGTH dropdown to select the network prefix.
• Click the dropdown (shows current value like /64)
• Range: /1 to /128
• Common values:
- /64 - Standard subnet/LAN (most common)
- /48 - Typical allocation to organizations
- /128 - Single host (loopback)

4

Understand prefix descriptions

The dropdown shows helpful descriptions for each prefix:
• /64 - Standard subnet/LAN - What you'll use for most networks
• Other prefixes show their typical use case
• This helps you choose the right prefix without memorizing

5

Calculate

If Auto-calculate is enabled, results appear as you type. Otherwise, click CALCULATE SUBNET. The stats bar shows - NETWORK PREFIX, LAST ADDRESS, TOTAL HOSTS, USABLE HOSTS, and SUBNETS.

6

Note the differences from IPv4

IPv6 results differ from IPv4:
• No broadcast address - IPv6 uses multicast instead
• Much larger host counts (astronomical numbers)
• Network prefix shown instead of network address
• Last address shown instead of broadcast

7

View IPv6 results

Results appear in the Overview, Binary view, and Subnet list tabs. IPv6 calculations show the network prefix, last address, and the vast number of available hosts in your subnet.

IPv6 mode with address input and prefix selection

The Overview tab displays your calculation results in easy-to-read cards. Each card shows one piece of network information with a copy button for quick access.

1

Access Overview tab

After calculating, click the Overview tab (first of three tabs). Six result cards appear in a grid layout, each displaying a specific network value.

2

NETWORK CLASS card

Shows which address class your IP belongs to (IPv4 only):
• Class A: First octet 1-126 (large networks)
• Class B: First octet 128-191 (medium networks)
• Class C: First octet 192-223 (small networks)
• Class D: Multicast addresses
• Class E: Reserved/experimental

3

CIDR NOTATION card

Displays the complete CIDR notation of your network:
• Example: 192.168.1.0/24
• Combines network address with prefix length
• Standard format used in routing and configuration
• Click the copy icon to copy this value

4

WILDCARD MASK card

Shows the inverse of your subnet mask:
• Example: 0.0.0.255 (for subnet 255.255.255.0)
• Used in ACLs (Access Control Lists) and some router configs
• Network bits become 0, host bits become 1
• Cisco routers often use wildcard masks

5

FIRST USABLE IP card

The first IP address you can assign to a device:
• Network address + 1
• Example: 192.168.1.1 (for 192.168.1.0/24)
• This is typically where you'd put your gateway/router
• Cannot use network address itself

6

LAST USABLE IP card

The last IP address you can assign to a device:
• Broadcast address - 1
• Example: 192.168.1.254 (for 192.168.1.0/24)
• Everything between first and last is assignable
• Cannot use broadcast address itself

7

IP TYPE card

Indicates whether the address is public or private:
• Private: Not routable on internet (10.x.x.x, 172.16-31.x.x, 192.168.x.x)
• Public: Routable on internet
• Loopback: 127.x.x.x (localhost)
• Link-local: 169.254.x.x (auto-assigned)

8

Copy individual values

Each card has a copy icon in the corner. Click it to copy that specific value to your clipboard. A notification confirms the copy. This is faster than selecting and copying text manually.

Overview tab with all calculation result cards

The Binary view tab shows the binary representation of addresses and masks. This is invaluable for understanding how subnetting actually works at the bit level.

1

Access Binary view tab

Click the Binary view tab (second of three tabs). This displays all network values in both decimal and binary format, side by side.

2

IP Address row

Shows your entered IP address:
• Left side: Decimal format (e.g., 192.168.1.100)
• Right side: Binary format (e.g., 11000000.10101000.00000001.01100100)
• Each octet is 8 bits, separated by dots
• Total of 32 bits for IPv4

3

Subnet mask row

Shows the subnet mask in binary:
• Example: 255.255.255.0 = 11111111.11111111.11111111.00000000
• Network bits are all 1s (contiguous from left)
• Host bits are all 0s (contiguous from right)
• The boundary between 1s and 0s defines the subnet

4

Network bits / Host bits bar

A visual bar shows the split between network and host portions:
• Orange/colored section: Network bits (e.g., 24 bits)
• Gray section: Host bits (e.g., 8 bits)
• Labels show the exact count: "Network bits: 24" / "Host bits: 8"
• This visualizes how the subnet mask divides the address

5

Network address row

Shows the network address in binary:
• The IP address with all host bits set to 0
• Example: 192.168.1.0 = 11000000.10101000.00000001.00000000
• Notice the last 8 bits are all zeros
• This identifies the subnet itself

6

Broadcast address row

Shows the broadcast address in binary:
• The IP address with all host bits set to 1
• Example: 192.168.1.255 = 11000000.10101000.00000001.11111111
• Notice the last 8 bits are all ones
• Packets sent here reach all hosts in subnet

7

Wildcard mask row

Shows the wildcard mask in binary:
• Inverse of subnet mask
• Example: 0.0.0.255 = 00000000.00000000.00000000.11111111
• Where subnet has 1s, wildcard has 0s and vice versa
• Used in router ACLs and some configurations

8

Learning from binary view

Use Binary view to understand:
• Why certain IPs are in the same subnet (matching network bits)
• How subnet size relates to host bits (more host bits = more hosts)
• How network/broadcast addresses are calculated (zeroing/maxing host bits)
• Why you lose 2 addresses per subnet (network + broadcast)

Binary view with network/host bits visualization

The Subnet list tab generates a list of available subnets within your network. This is incredibly useful for network planning and address allocation.

1

Access Subnet list tab

Click the Subnet list tab (third of three tabs). You'll see an "Available subnets" section with a count input field and Generate button.

2

Set number of subnets

In the count input field, enter how many subnets you want to generate:
• Enter a number (e.g., 10, 50, 100)
• Higher numbers show more subnets from the available range
• The maximum depends on your prefix length

3

Click Generate

Click the Generate button next to the count field. The calculator computes and displays a list of subnets based on your network configuration.

4

Understand the subnet list

Each subnet in the list shows:
• #number: Sequential subnet identifier (Subnet #1, #2, etc.)
• CIDR: The subnet in CIDR notation (e.g., 192.168.1.0/26)
• IP range: First to last usable IP
• Broadcast: The broadcast address for that subnet
• Hosts: Number of usable host addresses

Subnet list with available subnets and their details

5

Example: Splitting /24 into /26

If you have 192.168.1.0/24 and change to /26:
• A /24 has 256 addresses (254 usable)
• A /26 has 64 addresses (62 usable)
• You get 4 subnets from one /24
• List shows: 192.168.1.0/26, 192.168.1.64/26, 192.168.1.128/26, 192.168.1.192/26

6

Use cases for subnet lists

Generate subnet lists when:
• Planning office/department network segments
• Allocating VLANs in enterprise networks
• Designing cloud VPC subnets
• Creating DMZ and internal zone separation
• Documenting network architecture

Subnet #1:  192.168.1.0/26    | Range: .1-.62     | Broadcast: .63   | 62 hosts
Subnet #2:  192.168.1.64/26   | Range: .65-.126   | Broadcast: .127  | 62 hosts
Subnet #3:  192.168.1.128/26  | Range: .129-.190  | Broadcast: .191  | 62 hosts
Subnet #4:  192.168.1.192/26  | Range: .193-.254  | Broadcast: .255  | 62 hosts

The calculator includes a built-in CIDR Notation quick reference table. This saves you from having to memorize subnet masks and host counts.

1

Locate the reference table

Scroll down below the result tabs to find the CIDR Notation quick reference section. It displays a table organized by network class.

2

Class A section (/8 to /15)

Shows large network prefixes:
• /8: 255.0.0.0 - 16,777,214 hosts
• /9: 255.128.0.0 - 8,388,606 hosts
• Through /15: 255.254.0.0 - 131,070 hosts
• These are for major ISPs, large enterprises, or cloud providers

3

Class B section (/16 to /23)

Shows medium network prefixes:
• /16: 255.255.0.0 - 65,534 hosts
• /17: 255.255.128.0 - 32,766 hosts
• Through /23: 255.255.254.0 - 510 hosts
• Common for large organizations and data centers

4

Class C section (/24 to /32)

Shows small network prefixes:
• /24: 255.255.255.0 - 254 hosts (most common LAN)
• /25: 255.255.255.128 - 126 hosts
• /26: 255.255.255.192 - 62 hosts
• /27: 255.255.255.224 - 30 hosts
• /28: 255.255.255.240 - 14 hosts
• /29: 255.255.255.248 - 6 hosts
• /30: 255.255.255.252 - 2 hosts (point-to-point)
• /31: 255.255.255.254 - 2 hosts (special P2P)
• /32: 255.255.255.255 - 1 host (single host route)

5

Table columns explained

Each row in the table shows three pieces of information:
• CIDR: The prefix notation (e.g., /24)
• SUBNET MASK: The equivalent dotted decimal mask (e.g., 255.255.255.0)
• HOSTS: Number of usable host addresses (e.g., 254)

6

Using the reference table

Reference the table when:
• You need to convert between CIDR and subnet mask
• Planning how many hosts you can fit in a subnet
• Determining what prefix to use for a given number of devices
• Quick verification of your calculations

CIDR quick reference table organized by network class

The A, B, and C buttons provide quick access to common network class configurations. They filter the CIDR dropdown to show only relevant prefix lengths.

1

Class A button

Click the A button to load a Class A example:
• Loads IP: 10.0.0.0
• Loads mask: 255.0.0.0 (/8)
• First octet range: 1-126
• Use for: Very large networks, ISPs, cloud infrastructure
• Example networks: 10.0.0.0/8 (private), 44.0.0.0/8 (amateur radio)

2

Class B button

Click the B button to load a Class B example:
• Loads IP: 172.16.0.0
• Loads mask: 255.255.0.0 (/16)
• First octet range: 128-191
• Use for: Large organizations, universities, data centers
• Example networks: 172.16.0.0/12 (private range spans multiple /16s)

3

Class C button

Click the C button to load a Class C example:
• Loads IP: 192.168.1.0
• Loads mask: 255.255.255.0 (/24)
• First octet range: 192-223
• Use for: Small to medium networks, home/office LANs
• Example networks: 192.168.0.0/24, 192.168.1.0/24 (typical home networks)

Class buttons for quick network class selection

4

How class selection affects CIDR

When you click a class button:
• The IP address field is filled with a typical private IP for that class
• The subnet mask is set to the default for that class
• The CIDR dropdown is set to match the loaded mask
• Calculation runs automatically if auto-calculate is enabled

5

Note about classful vs. classless

Modern networking uses CIDR (Classless Inter-Domain Routing) which ignores traditional class boundaries. These buttons are a convenience feature - you can still use any prefix with any IP. The calculator doesn't enforce class rules; it just helps organize common choices.

Four action buttons in the upper right corner provide quick access to common operations. Each button has a specific function for managing your calculations.

1

Copy button

Click the Copy button (copy icon) to copy calculation results:
• Copies all current results to clipboard
• Formatted for easy pasting into documents
• Includes network address, mask, hosts, etc.
• A notification confirms successful copy

2

History button

Click the History button (clock icon) to view previous calculations:
• Opens a list of your past subnet calculations
• Shows IP, mask, and key results for each
• Click any entry to reload those values
• Useful for comparing different subnets or revisiting work

3

Download button

Click the Download button (download icon) to export results:
• Downloads calculation results as a file
• Useful for documentation or reporting
• Can be shared with colleagues or saved for reference
• Format is human-readable text

4

Delete button

Click the Delete button (trash icon) to clear current input:
• Resets all input fields to empty/default
• Clears current calculation results
• Does NOT delete history
• Use when starting a fresh calculation

Action buttons for managing calculations

The stats bar below the protocol tabs shows key metrics that update in real-time. Here's what each statistic means:

Subnetting fundamentals help you use the calculator effectively and interpret results correctly.

These are the most frequently used subnet masks with their characteristics and typical use cases.

Class A:  10.0.0.0/8        (10.0.0.0 - 10.255.255.255)
Class B:  172.16.0.0/12     (172.16.0.0 - 172.31.255.255)
Class C:  192.168.0.0/16    (192.168.0.0 - 192.168.255.255)

These ranges are reserved for private networks and are NOT
routed on the public internet. Use freely within your LAN.