Subnet CIDR Calculator
Network address, broadcast and usable host range from a CIDR block.
Enter your values
Enter the ip address you are working with.
Enter the cidr prefix in /bits.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Network address
- 192.168.1.0/24
- Broadcast address
- 192.168.1.255
- Subnet mask
- 255.255.255.0
- First usable host
- 192.168.1.1
- Last usable host
- 192.168.1.254
- Usable hosts
- 254
Quick answer
Number of usable hosts = 2^(32-prefix) - 2 for standard subnets.
hosts = 2^(32-prefix) - 2
At a glance
| What it does | Network address, broadcast and usable host range from a CIDR block. |
|---|---|
| Category | Technology |
| Inputs needed | IP address, CIDR prefix |
| Main output | Network address |
| Formula | hosts = 2^(32-prefix) - 2 |
| Cost | Free — no sign-up, no download |
How to use the Subnet CIDR Calculator
- 1Enter an IPv4 address inside the subnet.
- 2Enter the CIDR prefix length (e.g. /24 for a common 254-host subnet).
- 3Read the network address, broadcast address, usable host range and total host count.
Inputs explained
- IP address
- Enter the ip address you are working with.
- CIDR prefix(/bits)
- Enter the cidr prefix in /bits.
Worked example
Using the values the calculator loads with:
Inputs
- IP address192.168.1.50
- CIDR prefix24 /bits
Results
- Network address192.168.1.0/24
- Broadcast address192.168.1.255
- Subnet mask255.255.255.0
- First usable host192.168.1.1
- Last usable host192.168.1.254
- Usable hosts254
Frequently asked questions
What does /24 mean?
It means the first 24 bits are the network portion, leaving 8 bits (256 addresses, 254 usable) for hosts.
Why subtract 2 hosts?
The first address is the network address and the last is the broadcast address; both are reserved.
What do I need to enter into the Subnet CIDR Calculator?
Just 2 values: ip address, cidr prefix. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Subnet CIDR Calculator work out the answer?
Number of usable hosts = 2^(32-prefix) - 2 for standard subnets. It applies the formula hosts = 2^(32-prefix) - 2 and shows the working so you can check each step by hand.
Is the Subnet CIDR Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.