NET
Network Address
The lowest address in the subnet. It identifies the subnet itself on the wider network and is never assigned to a device.
Subnet Calculator
Subnet Calculator
Calculate IPv4 subnet information instantly from an IP address and CIDR prefix — network address, broadcast address, subnet mask and usable host range, worked out entirely in your browser.
Enter an IPv4 address and a CIDR prefix, or pick a common prefix below, then press Calculate.
- Free
- No signup required
- Runs entirely in your browser
Private IPv4 network
Network Address
—
Broadcast Address
—
Subnet Mask
—
Wildcard Mask
—
First Usable IP
—
Last Usable IP
—
Total Addresses
—
Usable Addresses
—
Host Bits
—
All values are calculated locally in your browser with standard IPv4 bitwise arithmetic — nothing is sent to a server.
The Basics
What Is a Subnet?
A smaller network carved out of a larger IPv4 address block.
A subnet is a smaller network carved out of a larger IPv4 address block. Splitting a network into subnets keeps broadcast traffic local, groups devices logically — by department, location or function — and lets you hand out only as many addresses as each segment actually needs.
Every IPv4 address is 32 bits long, written as four decimal numbers separated by dots (e.g. 192.168.1.25). A subnet mask — or, in CIDR notation, a prefix length like /24 — marks how many of those 32 bits belong to the network portion and how many are left for host addresses. The more bits assigned to the network, the fewer addresses remain for hosts, and the smaller the subnet.
Two addresses in every regular subnet are reserved: the network address, the lowest address in the range, identifies the subnet itself; the broadcast address, the highest address, is used to send data to every host on that subnet at once. Neither can be assigned to a device, which is why usable host addresses are normally two fewer than the subnet’s total address count.
Quick Start
How to Use the Subnet Calculator
Four steps, no installation and nothing sent to a server.
Enter an IPv4 address, such as
192.168.1.0.Enter a CIDR prefix, such as
24, or click one of the quick-pick options above the Calculate button.Click Calculate.
Review the network address, broadcast address, subnet mask and usable IP range in the results.
For example, entering 192.168.1.0 with a /24 prefix returns a network address of 192.168.1.0, a broadcast address of 192.168.1.255 and 254 usable addresses from 192.168.1.1 to 192.168.1.254. Once you have a device’s address, you can check whether it’s reachable with our Port Checker, or look up your own public address with What Is My IP.
Your Result
Understanding Subnet Calculator Results
What each value in the results above actually means.
BCAST
Broadcast Address
The highest address in the subnet, used to send a single message to every host on it at once. Like the network address, it can’t be assigned to a device.
MASK
Subnet Mask
A 32-bit value, written the same way as an IP address, that marks which bits of an address belong to the network and which belong to the host. /24 corresponds to 255.255.255.0.
MASK
Wildcard Mask
The inverse of the subnet mask — its host bits are 1s and its network bits are 0s. Used mainly in router access-control lists, where it plays the opposite role to a subnet mask.
IP
First Usable IP
The first address after the network address, and the lowest one a device can actually be assigned.
IP
Last Usable IP
The last address before the broadcast address, and the highest one a device can actually be assigned.
#
Total Addresses
The full size of the subnet — 2 raised to the number of host bits — including the network and broadcast addresses.
#
Usable Addresses
Total addresses minus the network and broadcast addresses: the number of devices the subnet can actually host. /31 and /32 subnets follow different rules — see the table below.
BITS
Host Bits
The number of bits left for host addresses once the CIDR prefix has claimed the network bits — 32 minus the prefix length. A /24 prefix leaves 8 host bits, for 256 total addresses.
CIDR
CIDR and Subnet Masks
Two ways of writing exactly the same information.
CIDR (Classless Inter-Domain Routing) notation writes a subnet mask as a prefix length instead of four numbers: a slash followed by how many of the address’s 32 bits belong to the network. /24 means the first 24 bits are the network portion, leaving 8 bits (32 − 24) for hosts.
A /24 prefix is the same thing as a 255.255.255.0 subnet mask: 256 total addresses, of which 254 are usable once the network and broadcast addresses are set aside. If you also need to plan link capacity or transfer times for a network this size, see our Bandwidth Calculator.
Example: 192.168.1.0/24
Network
192.168.1.0
Broadcast
192.168.1.255
Subnet Mask
255.255.255.0
Usable Range
192.168.1.1 – 192.168.1.254
Total
256
Usable
254
The /24 prefix reserves the first three octets (192.168.1) for the network, leaving the last octet — 0 to 255 — for hosts. Two of those 256 values are reserved: 0 for the network address and 255 for the broadcast address, leaving 254 addresses that can be assigned to devices.
Reference
IPv4 Subnet Table
Subnet mask, wildcard mask and address counts for every common IPv4 prefix.
| CIDR | Subnet Mask | Wildcard Mask | Total Addresses | Usable Hosts |
|---|---|---|---|---|
| /16 | 255.255.0.0 | 0.0.255.255 | 65,536 | 65,534 |
| /17 | 255.255.128.0 | 0.0.127.255 | 32,768 | 32,766 |
| /18 | 255.255.192.0 | 0.0.63.255 | 16,384 | 16,382 |
| /19 | 255.255.224.0 | 0.0.31.255 | 8,192 | 8,190 |
| /20 | 255.255.240.0 | 0.0.15.255 | 4,096 | 4,094 |
| /21 | 255.255.248.0 | 0.0.7.255 | 2,048 | 2,046 |
| /22 | 255.255.252.0 | 0.0.3.255 | 1,024 | 1,022 |
| /23 | 255.255.254.0 | 0.0.1.255 | 512 | 510 |
| /24 | 255.255.255.0 | 0.0.0.255 | 256 | 254 |
| /25 | 255.255.255.128 | 0.0.0.127 | 128 | 126 |
| /26 | 255.255.255.192 | 0.0.0.63 | 64 | 62 |
| /27 | 255.255.255.224 | 0.0.0.31 | 32 | 30 |
| /28 | 255.255.255.240 | 0.0.0.15 | 16 | 14 |
| /29 | 255.255.255.248 | 0.0.0.7 | 8 | 6 |
| /30 | 255.255.255.252 | 0.0.0.3 | 4 | 2 |
| /31 | 255.255.255.254 | 0.0.0.1 | 2 | 2 * |
| /32 | 255.255.255.255 | 0.0.0.0 | 1 | 1 † |
* A /31 has no separate network or broadcast address; both addresses are usable under RFC 3021, typically for point-to-point links. † A /32 identifies a single host, so its one address is both the network address and the usable address.
Keep Diagnosing
More Network Tools
A subnet range is one piece of the picture. These tools look at the rest of your network.
IP
What Is My IP
Find your public IP address instantly.
ResultPublic IPv4 / IPv6 address
DNS
DNS Lookup
Check DNS records for any domain.
ResultA, AAAA, MX, TXT, NS & CNAME records
Ports
Port Checker
Check whether a port is open and reachable from the Internet.
ResultOpen or closed status
Capacity
Bandwidth Calculator
Estimate the bandwidth you need, or how long a file will take to transfer at a given speed.
ResultRequired Mbps or transfer time
Latency
Ping Test
Measure the response time between your device and our test server.
ResultRound-trip time in ms
Speed
Internet Speed Test
Check your download speed, upload speed and connection latency.
ResultDownload & upload in Mbps, ping in ms
FAQ
Subnet Calculator FAQ
Short answers to the questions people ask most about subnets and subnet calculators.
What is a subnet calculator?
A subnet calculator works out an IPv4 subnet’s network address, broadcast address, subnet mask, wildcard mask and usable host range from just an IP address and a CIDR prefix, so you don’t have to do the binary math by hand.
How do I calculate a subnet?
Enter an IP address and a CIDR prefix above and press Calculate. The tool applies the subnet mask to the address with a bitwise AND to find the network address, then works out the broadcast address, the first and last usable IPs, and the number of usable hosts from there.
What is a subnet mask?
A subnet mask is a 32-bit value, written like an IP address (e.g. 255.255.255.0), that marks which bits of an address are the network portion and which are the host portion. It does the same job as a CIDR prefix, just in a different format.
What does /24 mean in an IP address?
/24 is CIDR notation for a subnet mask of 255.255.255.0. It means the first 24 of the address’s 32 bits identify the network, leaving 8 bits — 256 addresses — for hosts.
How many hosts are in a /24 subnet?
254. A /24 subnet has 256 total addresses, but the first (the network address) and the last (the broadcast address) can’t be assigned to a device, leaving 254 usable addresses.
What is the difference between CIDR and subnet mask?
They describe the same thing in two formats. A subnet mask is written as four decimal numbers, e.g. 255.255.255.0; CIDR notation writes the same value as a prefix length, e.g. /24 — the count of network bits set to 1 in the mask.
What is the network address?
The network address is the lowest address in a subnet — the address you get by applying the subnet mask to any address in that subnet. It identifies the subnet as a whole and can’t be assigned to a device.
What is the broadcast address?
The broadcast address is the highest address in a subnet. Sending data to it delivers that data to every host on the subnet at once. Like the network address, it’s reserved and can’t be assigned to a device.
Can I calculate an IPv4 subnet online?
Yes — enter an IPv4 address and CIDR prefix above. The calculation runs entirely in your browser, so nothing is sent to a server. You can look up your own address first with our What Is My IP tool.
How many usable IP addresses are in a subnet?
Usually the subnet’s total address count minus 2, for the reserved network and broadcast addresses. The exceptions are /31 subnets, which have 2 usable addresses under RFC 3021, and /32 subnets, which represent a single usable address.
Get started
Calculate a Subnet
Scroll up, enter an IPv4 address and CIDR prefix, and get your network details instantly.