IP Subnet Calculator
Calculate network address, broadcast IP, host range, and subnet mask from any CIDR notation.
How to use
- 1 Enter an IP address in CIDR notation (e.g. 192.168.1.0/24) into the input field.
- 2 Click Calculate and the tool computes the network address, broadcast address, subnet mask, and usable host range.
- 3 Check the number of usable host addresses for your subnet prefix.
- 4 Use the results to plan your network topology or configure firewall rules.
Key features
- Calculates network address, broadcast, subnet mask, and usable host range
- Supports all CIDR prefixes from /0 to /32
- Shows the number of usable host addresses
- Useful for network planning, firewall rules, and cloud VPC configuration
What is CIDR Notation?
CIDR (Classless Inter-Domain Routing) is the compact way to describe an IP network. 192.168.0.0/24 means "192.168.0.x, all 256 addresses where the first 24 bits are fixed." The number after the slash is the prefix length: the higher it is, the smaller the network.
CIDR replaced the old Class A/B/C system in 1993 (RFC 1519), enabling more efficient use of the IPv4 address space. Every cloud platform: AWS VPCs, GCP subnets, Azure VNets, uses CIDR notation to define network boundaries.
Common Use Cases
Cloud VPC and subnet design
Calculate available host ranges before creating subnets in AWS, GCP, or Azure to avoid overlap.
Firewall rules and allowlists
Verify that a CIDR block covers the right range of IPs before adding it to a security group or firewall.
Office network planning
Determine how many usable host addresses fit in a planned subnet before allocating address space.
VPN split tunneling config
Calculate the exact network address and mask needed for routing table entries in a VPN client.
Networking study and practice
Check your manual subnetting calculations against this tool while studying for CCNA or CompTIA Network+.
Zero Trust access policies
Verify that IP-based access conditions in IAM policies reference the correct CIDR blocks.
Common Subnet Sizes
The prefix lengths you'll encounter most in cloud and on-premises networking.
| CIDR | Usable hosts | Typical use |
|---|---|---|
| /32 | 1 | Single host firewall rule |
| /30 | 2 | Point-to-point link |
| /28 | 14 | Small cloud subnet |
| /24 | 254 | Standard LAN, office network |
| /16 | 65,534 | AWS/GCP VPC default (10.0.0.0/16) |
| /8 | 16,777,214 | Large private network (10.x.x.x) |
Frequently Asked Questions
How do I calculate a subnet from an IP and CIDR?
Enter an IP address followed by a forward slash and the prefix length (e.g. 192.168.1.0/24). The calculator will show you the network address, broadcast address, subnet mask, usable host range, and total number of hosts. The prefix length tells you how many bits are fixed: /24 means the first 24 bits are the network portion, leaving 8 bits for hosts.
What does /24 mean in IP addressing?
/24 is a CIDR prefix length indicating that the first 24 bits of the IP address are the network portion, leaving 8 bits (256 addresses) for hosts. A /24 subnet has 254 usable host addresses (256 minus network and broadcast addresses). It's the most common subnet size in office networks and corresponds to the subnet mask 255.255.255.0.
How many usable hosts are in a /28 subnet?
A /28 subnet has 16 total addresses (32 bits − 28 = 4 bits → 2⁴ = 16). After subtracting the network address (first) and broadcast address (last), you get 14 usable hosts. This is a common size for small cloud subnets in AWS, GCP, and Azure.
What's the difference between network address and broadcast address?
The network address (first address in the range) identifies the subnet itself and cannot be assigned to a host. The broadcast address (last address in the range) is used to send packets to all hosts in the subnet simultaneously. For example, in 192.168.1.0/24, the network address is 192.168.1.0 and the broadcast address is 192.168.1.255.
How do I find my subnet mask?
On Windows, run ipconfig and look for "Subnet Mask". On macOS/Linux, run ifconfig or ip addr and look for netmask. You can also enter your IP and CIDR notation into this calculator: it will display the subnet mask in dotted decimal format (e.g. 255.255.255.0 for /24).