IP Subnet Calculator: calculate IPv4 networks and CIDR instantly
Enter an IPv4 address with a CIDR prefix or subnet mask and instantly get the network address, broadcast, host range, number of hosts and wildcard mask, including splitting into smaller subnets.
- 100% free
- No sign-up
- Your data stays in your browser
- Real-time results
Calculate a subnet
Split the network into subnets
| # | Network | Usable range | Broadcast |
|---|
IP Subnet Calculator: how it works in 3 steps
Enter an IP address
For example 192.168.1.10/24 or 10.0.0.5 255.255.0.0. Both notations are recognised.
Choose the prefix
Pick the CIDR prefix or subnet mask from the list if you did not type it in.
Read the result
All values are calculated instantly. Optionally split the network into smaller subnets.
Subnetting explained simply
An IPv4 address has 32 bits, written as four numbers from 0 to 255 (e.g. 192.168.1.10). The subnet mask, or simply the CIDR prefix such as /24, splits these bits into a network part and a host part. All devices with the same network part are in the same subnet and reach each other directly, without a router.
The larger the prefix, the smaller the network: a /24 offers 254 usable addresses, a /30 only 2, typical for point-to-point links between routers.
CIDR table: the most common prefixes
| CIDR | Subnet mask | Addresses | Usable hosts |
|---|---|---|---|
/8 | 255.0.0.0 | 16,777,216 | 16,777,214 |
/16 | 255.255.0.0 | 65,536 | 65,534 |
/20 | 255.255.240.0 | 4,096 | 4,094 |
/21 | 255.255.248.0 | 2,048 | 2,046 |
/22 | 255.255.252.0 | 1,024 | 1,022 |
/23 | 255.255.254.0 | 512 | 510 |
/24 | 255.255.255.0 | 256 | 254 |
/25 | 255.255.255.128 | 128 | 126 |
/26 | 255.255.255.192 | 64 | 62 |
/27 | 255.255.255.224 | 32 | 30 |
/28 | 255.255.255.240 | 16 | 14 |
/29 | 255.255.255.248 | 8 | 6 |
/30 | 255.255.255.252 | 4 | 2 |
/31 | 255.255.255.254 | 2 | 2 |
/32 | 255.255.255.255 | 1 | 1 |
Private IP ranges (RFC 1918)
10.0.0.0/8(10.0.0.0 – 10.255.255.255)172.16.0.0/12(172.16.0.0 – 172.31.255.255)192.168.0.0/16(192.168.0.0 – 192.168.255.255)
These addresses are not routed on the internet and are meant for home and company networks.
IP Subnet Calculator: your benefits
Real-time results
Every keystroke is calculated instantly, with no submit and no reload.
CIDR and subnet mask
Type /24 or 255.255.255.0: the calculator understands both.
Split subnets
Divide a network into equal subnets and see every range at a glance.
Binary view
IP address and mask are shown in binary, great for learning and exams.
Frequently asked questions about the IP Subnet Calculator tool
What is a subnet?
A subnet is a part of an IP network. The subnet mask defines which part of an IP address identifies the network and which part identifies the individual host.
What does /24 mean in CIDR notation?
The number after the slash is the number of network bits. /24 equals the subnet mask 255.255.255.0 and provides 254 usable host addresses.
Why are only 254 hosts usable in a /24?
Two of the 256 addresses are reserved: the network address (e.g. 192.168.1.0) and the broadcast address (e.g. 192.168.1.255).
What is a wildcard mask?
A wildcard mask is the inverted subnet mask (e.g. 0.0.0.255 for /24). It is mainly used in Cisco ACLs and OSPF.
Does the calculator support IPv6?
Currently the calculator handles IPv4 networks. An IPv6 calculator is planned.
More free online tools
JPG to PDF
Combine photos, scans and screenshots (JPG, PNG, WebP) into one PDF file.
Open tool →PDF to JPG
Save every PDF page as a JPG or PNG image, up to 300 DPI, also as ZIP.
Open tool →Merge PDF
Combine several PDF files in any order into one PDF.
Open tool →Image Resizer
Reduce images in pixel size and file size, several at once, as JPG, PNG or WebP.
Open tool →QR Code Generator
Create QR codes for links, contacts and WiFi. The WiFi code connects phones with one scan.
Open tool →JSON Formatter
Format, validate and minify JSON, with errors shown by line and column.
Open tool →Keep an eye on your network
TKB Monitor watches your servers, devices and services and alerts you before small problems slow your work down.