IP Address Calculator
An IP Address Calculator is a useful networking tool for determining important details about an IPv4 subnet. By entering an IPv4 address and either a subnet mask or CIDR notation, you can calculate the network address, broadcast address, first usable IP, last usable IP, and total hosts.
Whether you are learning networking, configuring a local network, planning an IP addressing scheme, or troubleshooting subnet information, an IP calculator can make subnet calculations much faster than doing them manually.
This IP Address Calculator supports standard IPv4 addresses such as 192.168.1.1 and subnet masks such as 255.255.255.0. You can also enter a CIDR prefix such as /24 by entering 24 in the CIDR field.
What Is an IP Address?
An IP address, or Internet Protocol address, identifies a device or network interface on an IP network. IPv4 addresses consist of four decimal octets separated by periods.
For example:
192.168.1.1
Each octet can contain a value from 0 through 255.
An IPv4 address contains 32 bits. A subnet mask determines which portion of those bits identifies the network and which portion is available for host addresses.
For example:
- IP address:
192.168.1.25 - Subnet mask:
255.255.255.0 - CIDR notation:
/24
The /24 indicates that the first 24 bits are used for the network portion, leaving 8 bits for hosts.
What Does This IP Address Calculator Calculate?
After you enter the IP address and subnet information, the calculator provides five results:
- Network Address
- Broadcast Address
- First Usable IP
- Last Usable IP
- Total Hosts
These values are commonly used when configuring networks and determining the address range available within an IPv4 subnet.
How to Use the IP Address Calculator
Using the calculator is straightforward.
Step 1: Enter the IP Address
Enter an IPv4 address in the IP Address field.
For example:
192.168.1.100
The calculator checks that the address follows the four-octet IPv4 format and that every octet is between 0 and 255.
Step 2: Enter a Subnet Mask
You can enter a subnet mask such as:
255.255.255.0
The calculator uses this mask to determine the network and broadcast addresses.
Step 3: Or Enter CIDR Notation
Instead of entering a subnet mask, you can enter a CIDR prefix such as:
24
This represents:
255.255.255.0
Common examples include:
| CIDR | Subnet Mask |
|---|---|
| /8 | 255.0.0.0 |
| /16 | 255.255.0.0 |
| /24 | 255.255.255.0 |
| /25 | 255.255.255.128 |
| /26 | 255.255.255.192 |
| /27 | 255.255.255.224 |
| /28 | 255.255.255.240 |
| /29 | 255.255.255.248 |
| /30 | 255.255.255.252 |
If a CIDR value is entered, the calculator uses it instead of the subnet mask field.
Step 4: Click Calculate
Click Calculate to display the subnet information.
The calculator then shows the calculated network address, broadcast address, first usable address, last usable address, and total host count.
What Is a Network Address?
The network address identifies the subnet itself.
It is obtained by performing a bitwise AND operation between the IP address and the subnet mask.
For example:
IP: 192.168.1.100
Mask: 255.255.255.0
The resulting network address is:
192.168.1.0
The network address is not normally assigned to an individual host because it represents the entire subnet.
What Is a Broadcast Address?
The broadcast address is the address used to represent all hosts on a particular IPv4 subnet.
For a typical /24 network:
- Network:
192.168.1.0 - Broadcast:
192.168.1.255
The addresses between them are generally used for individual hosts.
The calculator determines the broadcast address by taking the calculated network address and setting the host bits to 1.
What Is the First Usable IP?
The first usable IP is calculated by adding 1 to the network address.
For example:
- Network address:
192.168.1.0 - First usable IP:
192.168.1.1
This is commonly the first host address available within a conventional IPv4 subnet.
What Is the Last Usable IP?
The last usable IP is calculated by subtracting 1 from the broadcast address.
For example:
- Broadcast address:
192.168.1.255 - Last usable IP:
192.168.1.254
Therefore, a typical /24 subnet has the following structure:
- Network:
192.168.1.0 - First host:
192.168.1.1 - Last host:
192.168.1.254 - Broadcast:
192.168.1.255
What Is CIDR Notation?
CIDR stands for Classless Inter-Domain Routing.
CIDR notation represents an IPv4 network by placing a slash followed by the number of network bits after the IP address.
For example:
192.168.1.0/24
The /24 means that 24 of the IPv4 address’s 32 bits belong to the network portion.
That leaves:
32 − 24 = 8 host bits
The calculator accepts CIDR values from 0 through 32.
Understanding Host Bits
An IPv4 address contains 32 bits.
The number of host bits can be determined using:
Host Bits = 32 − Network Bits
For example, with /24:
32 − 24 = 8 host bits
With /26:
32 − 26 = 6 host bits
With /28:
32 − 28 = 4 host bits
More host bits mean more possible addresses within a subnet, while fewer host bits mean a smaller subnet.
How Is Total Hosts Calculated?
For a conventional subnet, the number of usable host addresses is commonly calculated as:
Usable Hosts = 2^Host Bits − 2
The two addresses excluded are generally the network address and broadcast address.
For a /24 network:
Host Bits = 8
Therefore:
2^8 − 2 = 254
So a typical /24 subnet has 254 usable host addresses.
For /26:
2^6 − 2 = 62
For /27:
2^5 − 2 = 30
For /28:
2^4 − 2 = 14
This calculator uses that 2^host bits − 2 formula for its Total Hosts result.
IP Address Calculator Example: /24 Network
Suppose you enter:
IP Address: 192.168.1.100
Subnet Mask: 255.255.255.0
The calculator produces:
- Network Address:
192.168.1.0 - Broadcast Address:
192.168.1.255 - First Usable IP:
192.168.1.1 - Last Usable IP:
192.168.1.254 - Total Hosts:
254
The same subnet can be represented using:
192.168.1.100/24
because 255.255.255.0 corresponds to /24.
IP Address Calculator Example: /26 Network
Consider:
IP Address: 192.168.1.70
CIDR: 26
A /26 provides 6 host bits and 64 total addresses.
Using the conventional network structure, the relevant subnet is:
- Network Address:
192.168.1.64 - Broadcast Address:
192.168.1.127 - First Usable IP:
192.168.1.65 - Last Usable IP:
192.168.1.126 - Total Hosts:
62
This demonstrates how changing the prefix from /24 to /26 creates smaller subnets.
IP Address Calculator Example: /16 Network
Suppose you enter:
IP Address: 172.16.25.50
CIDR: 16
The corresponding subnet mask is:
255.255.0.0
The network address is:
172.16.0.0
The broadcast address is:
172.16.255.255
A /16 leaves 16 host bits, resulting in:
2^16 − 2 = 65,534 usable hosts
This is considerably larger than a /24 subnet.
Subnet Mask vs. CIDR Notation
A subnet mask and CIDR notation communicate the same basic subnet boundary in different formats.
For example:
Subnet Mask: 255.255.255.0
CIDR: /24
Another example:
Subnet Mask: 255.255.255.192
CIDR: /26
The dotted-decimal subnet mask is often familiar to people configuring network devices, while CIDR notation provides a compact way to describe the same network prefix.
Why Is Subnetting Important?
Subnetting divides an IP address space into smaller logical networks.
This can be useful for:
- Organizing devices
- Separating network segments
- Managing IP address allocation
- Reducing unnecessary broadcast traffic
- Designing local networks
- Planning network infrastructure
- Understanding routing
- Troubleshooting connectivity
For example, instead of putting every device into one large network, an organization can use different subnets for different departments, locations, or network functions.
Private IPv4 Address Ranges
Many local networks use private IPv4 address ranges.
The commonly used private ranges are:
10.0.0.0/8172.16.0.0/12192.168.0.0/16
An address such as 192.168.1.100 is therefore commonly encountered in home and small-office networks.
Private IP addresses are intended for use within private networks and are not directly routable across the public internet in the same way as public IPv4 addresses.
Network Address vs. Host Address
It is important to distinguish between a network address and a host address.
Consider:
192.168.1.0/24
Here:
192.168.1.0identifies the network.192.168.1.1through192.168.1.254are conventional host addresses.192.168.1.255is the broadcast address.
The calculator helps identify these boundaries from the IP address and subnet information.
Common CIDR Prefixes
Here are some frequently encountered IPv4 prefixes:
| CIDR | Host Bits | Usable Hosts |
|---|---|---|
| /16 | 16 | 65,534 |
| /20 | 12 | 4,094 |
| /24 | 8 | 254 |
| /25 | 7 | 126 |
| /26 | 6 | 62 |
| /27 | 5 | 30 |
| /28 | 4 | 14 |
| /29 | 3 | 6 |
| /30 | 2 | 2 |
The calculator’s total-host calculation follows the conventional 2^host bits − 2 approach.
Important Calculator Limitations
This calculator is designed around standard IPv4 subnet calculations, but there are some important edge cases to understand.
The tool checks that each IP and subnet-mask octet is between 0 and 255, but it does not explicitly validate that a manually entered subnet mask contains contiguous network bits. For example, unusual non-contiguous masks may therefore produce mathematical results even though they are not standard CIDR subnet masks.
The calculator also calculates the first usable address by adding 1 to the final octet and the last usable address by subtracting 1 from the final octet. This works for ordinary subnets such as /24, but special prefixes such as /31 and /32 require different treatment in practical networking.
The standard host formula also assumes the conventional model where network and broadcast addresses are excluded.
For general subnet planning, the results are most useful with conventional IPv4 subnet masks.
Frequently Asked Questions
1. What is an IP Address Calculator?
An IP Address Calculator is a networking tool that calculates subnet information from an IPv4 address and subnet mask or CIDR prefix. This calculator provides network, broadcast, first usable, last usable, and total host information.
2. What is a subnet mask?
A subnet mask identifies which portion of an IPv4 address belongs to the network and which portion is available for hosts. A common example is 255.255.255.0, which corresponds to /24.
3. What does /24 mean?
A /24 CIDR prefix means that 24 of the 32 IPv4 bits are used for the network portion. The remaining 8 bits are available for host addressing.
4. How many usable hosts are in a /24 subnet?
Using the conventional host calculation, a /24 has 8 host bits and provides 254 usable host addresses.
5. What is the network address?
The network address identifies the subnet itself. It is calculated by applying the subnet mask to the IP address using a bitwise AND operation.
6. What is the broadcast address?
The broadcast address is the address associated with all host bits being set to 1. In a conventional IPv4 subnet, it is used to address all hosts on that subnet.
7. What is the first usable IP address?
For a conventional subnet, the first usable IP is normally one address after the network address. For example, if the network is 192.168.1.0, the first usable address is 192.168.1.1.
8. What is the last usable IP address?
For a conventional subnet, the last usable IP is normally one address before the broadcast address. If the broadcast address is 192.168.1.255, the last usable address is 192.168.1.254.
9. Can I use CIDR notation instead of a subnet mask?
Yes. The calculator allows you to enter a CIDR value from 0 to 32. For example, entering 24 corresponds to a /24 prefix.
10. What is the subnet mask for /26?
The standard subnet mask for /26 is 255.255.255.192. It leaves 6 host bits and provides 62 conventional usable host addresses.
11. How many hosts does a /28 subnet have?
A /28 leaves 4 host bits. Using the conventional formula, it provides 14 usable host addresses.
12. What is the difference between an IP address and a network address?
An IP address can identify a particular network interface or host, while the network address identifies the subnet containing those hosts. The subnet mask determines the boundary between the network and host portions.
13. Can this calculator calculate IPv6 addresses?
No. This calculator is designed for IPv4, which uses 32-bit addresses written as four decimal octets. IPv6 uses a different 128-bit addressing system.
14. Why does the calculator ask for both a subnet mask and CIDR notation?
The calculator supports both common ways of describing an IPv4 subnet. You can provide a dotted-decimal subnet mask such as 255.255.255.0 or use a CIDR value such as 24. If a CIDR value is entered, the calculator uses it to generate the mask.
15. What is the formula for calculating usable IPv4 hosts?
For a conventional subnet, the calculator uses 2^host bits − 2. The host bits are the 32 IPv4 bits that are not part of the network prefix. The subtraction accounts for the conventional network and broadcast addresses.
Final Thoughts
The IP Address Calculator provides a quick way to understand the structure of an IPv4 subnet. Enter an IPv4 address along with a subnet mask or CIDR prefix, and the tool calculates the network address, broadcast address, first usable IP, last usable IP, and total host count.
Understanding these values is fundamental to IPv4 networking. Whether you are working with a home network, studying subnetting, configuring network equipment, or planning an IP address range, knowing how the network and host portions of an address work can make network configuration much easier.