Subnet Calculator
Work out network address, broadcast address, and usable host range from an IP and CIDR (or subnet mask). Handy for network design, firewall rules, and understanding IP ranges. Runs in your browser — no data sent to a server.
Calculate Subnet
Enter an IPv4 address and CIDR (e.g. /24), then click Get subnet.
Result
| Network | 192.168.1.0 |
|---|---|
| Broadcast | 192.168.1.255 |
| Subnet mask | 255.255.255.0 |
| Wildcard | 0.0.0.255 |
| First host | 192.168.1.1 |
| Last host | 192.168.1.254 |
| Usable hosts | 254 |
What Is a Subnet Calculator?
A subnet calculator takes an IP address and a subnet mask (or CIDR prefix like /24) and figures out the network address, broadcast address, and the range of usable host IPs in that subnet. That’s useful when you’re designing networks, writing firewall rules, or debugging “why can’t this host reach that one.”
CIDR (e.g. /24) tells you how many bits are the “network” part. The rest are for hosts. A /24 gives 256 addresses (254 usable); a /28 gives 16 (14 usable). Our IP lookup and What is my IP don’t do subnet math — they show geolocation and ISP. For hostname (reverse DNS), use reverse DNS lookup.
How to Use the Subnet Calculator
Enter any private or public IPv4 address and a CIDR (0–32). The calculator updates as you type. You’ll see network, broadcast, mask, first/last host, and usable host count. No signup; everything runs in your browser. For checking if an IP is valid or public/private, try our IP address validator (or IP lookup for live lookup).
Features
- Network and broadcast address
- Subnet mask and wildcard
- First and last usable host
- Usable host count; runs locally
Why Use This Tool
Network admins use it to plan subnets and check firewall rules. Developers use it to validate allowed IP ranges. Pair with ping test or traceroute tool for connectivity, or DNS lookup for domain setup.
FAQs
What is a subnet calculator?
A subnet calculator takes an IP address and subnet mask (or CIDR) and computes the network address, broadcast address, usable host range, and number of hosts.
What is CIDR?
CIDR (Classless Inter-Domain Routing) is notation like /24 that shows how many bits are the network part. /24 means 24 bits for network, 8 for hosts (256 addresses, 254 usable).
How many hosts in a /24?
A /24 has 256 addresses. Subtract 2 (network and broadcast) = 254 usable host addresses.
Is the subnet calculator free?
Yes. Our calculator runs in your browser. No signup, no data sent to a server.
Does it support IPv6?
This version is for IPv4. IPv6 subnetting uses longer prefixes (e.g. /64); we may add an IPv6 calculator later.