Subnet Calculator
Enter an IPv4 CIDR block to calculate the network, broadcast, usable host range, and host count.
Example: 10.0.0.0/8, 172.16.0.0/16, 192.168.1.0/24
Network Address
192.168.1.0
Broadcast Address
192.168.1.255
Subnet Mask
255.255.255.0
Wildcard Mask
0.0.0.255
Used in Cisco ACLs
First Host
192.168.1.1
Last Host
192.168.1.254
Usable Hosts
254
Total Addresses
256
incl. network + broadcast
Prefix Length
/24
Address Space Map
Bit allocation — /24
About
What is a Subnet Calculator?
A subnet calculator is an essential tool for network engineers and administrators who need to plan, design, or troubleshoot IP networks. It takes an IPv4 address combined with a CIDR prefix length and computes all relevant network parameters instantly.
CIDR (Classless Inter-Domain Routing) notation expresses an IP address and its associated subnet mask as a single string, such as 192.168.1.0/24. The number after the slash indicates how many bits are used for the network portion of the address, with the remaining bits available for host addresses.
Network engineers use subnetting to divide large IP address spaces into smaller, more manageable segments. This is critical for improving security through network isolation, optimizing routing efficiency, and ensuring scalable infrastructure design in enterprise and cloud environments.
Whether you are designing VLANs, configuring firewalls, allocating address space for cloud VPCs, or simply studying for a networking certification, understanding subnet boundaries and host ranges is a fundamental skill.
Guide
How to Use This Tool
- 1.Enter an IPv4 address in CIDR notation into the input field, for example 10.0.0.0/8 or 192.168.1.0/24.
- 2.Results update automatically — no button press required. You will see the network address, broadcast address, subnet mask, wildcard mask, first and last usable host IPs, and total host count.
- 3.Use the Copy button to copy all results to your clipboard, or Export CSV to download a spreadsheet-ready file for documentation or reporting.
- 4.The URL updates automatically with your CIDR — share it directly with a colleague to load the same calculation instantly.
- 5.Save results to your dashboard using the Save button if you are logged in, so you can reference them later alongside other calculations.
FAQ
Frequently Asked Questions
What does /24 mean in an IP address?+
The /24 is the CIDR prefix length — the first 24 bits identify the network, leaving 8 bits for hosts. A /24 gives you 254 usable addresses (256 total minus the network and broadcast addresses).
What is the difference between subnet mask and wildcard mask?+
A subnet mask (e.g. 255.255.255.0) marks which bits are the network portion. A wildcard mask is its bitwise inverse (0.0.0.255) — used in Cisco ACLs and OSPF to specify which bits to ignore when matching.
What is a broadcast address?+
The broadcast address is the last address in a subnet. Sending to it delivers the packet to all hosts in that subnet. It cannot be assigned to a host, just like the network address (the first address).
How many hosts does a /24 subnet support?+
254 usable hosts. Total address space is 256 (2^8), minus the network address and broadcast address. Use a /23 for 510 hosts, or a /25 for 126.
What are RFC 1918 private IP ranges?+
RFC 1918 defines three private IP ranges not routable on the public internet: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. These are used in internal networks, VPNs, and cloud VPCs.
Can I share a subnet calculation with a colleague?+
Yes — the URL updates automatically as you type. Copy the URL from your browser and send it; your colleague will open the exact same calculation.
Reference
Common CIDR Blocks
These are the most frequently used CIDR prefix lengths in network design, from large enterprise backbones down to individual host routes.
| CIDR | Subnet Mask | Usable Hosts | Typical Use |
|---|---|---|---|
| /8 | 255.0.0.0 | 16,777,214 | Large ISP or enterprise backbone |
| /16 | 255.255.0.0 | 65,534 | Campus or regional network |
| /24 | 255.255.255.0 | 254 | Standard office or VLAN segment |
| /28 | 255.255.255.240 | 14 | Small subnet or cloud VPC tier |
| /32 | 255.255.255.255 | 1 | Single host route or loopback |