Subnet Calculator
Calculate network address, broadcast, usable host range, and subnet mask from CIDR notation.
Results
Network Address
10.0.1.0
Broadcast Address
10.0.1.255
First Usable Host
10.0.1.1
Last Usable Host
10.0.1.254
Subnet Mask
255.255.255.0
Wildcard Mask
0.0.0.255
Total Usable Hosts
254
CIDR Notation
10.0.1.0/24
Common Subnet Sizes
| CIDR | Mask | Hosts | Use Case |
|---|---|---|---|
| /32 | 255.255.255.255 | 1 | Single host |
| /28 | 255.255.255.240 | 14 | Small subnet |
| /26 | 255.255.255.192 | 62 | Small team |
| /24 | 255.255.255.0 | 254 | Standard subnet |
| /20 | 255.255.240.0 | 4,094 | Large VPC subnet |
| /16 | 255.255.0.0 | 65,534 | VPC CIDR block |
What is a Subnet Calculator?
A subnet calculator helps you divide IP networks into smaller, manageable segments using CIDR (Classless Inter-Domain Routing) notation. CIDR notation combines an IP address with a prefix length (like 10.0.0.0/24) that indicates how many bits define the network portion. The remaining bits identify individual hosts within that subnet. Subnetting is fundamental to network design, enabling efficient IP address allocation, traffic isolation, and security boundary enforcement.
DevOps engineers and cloud architects use subnet calculators daily when designing VPC architectures on AWS, Azure, or GCP. Common use cases include planning VPC CIDR blocks, sizing subnets for public and private tiers, calculating available host addresses for auto-scaling groups, and configuring security group rules. Understanding CIDR notation is essential for infrastructure-as-code tools like Terraform, CloudFormation, and Pulumi where subnet definitions directly impact deployment success.
Frequently Asked Questions
How many hosts in a /24?
A /24 subnet provides 254 usable host addresses. The total address space is 256 (2^8), but two addresses are reserved: the network address (first) and the broadcast address (last). This is the most common subnet size for standard network segments and is equivalent to a 255.255.255.0 subnet mask.
What is the difference between /16 and /24?
A /16 subnet has 65,534 usable hosts while a /24 has only 254. The prefix number indicates how many bits are used for the network portion—/16 uses 16 bits leaving 16 for hosts, while /24 uses 24 bits leaving only 8 for hosts. A /16 is commonly used as a VPC CIDR block, while /24 subnets are used for individual application tiers within that VPC.
What is a broadcast address?
The broadcast address is the last address in a subnet and is used to send data to all hosts on that network simultaneously. For example, in the 192.168.1.0/24 network, the broadcast address is 192.168.1.255. It cannot be assigned to any device. In cloud networking, broadcast is typically disabled, but understanding the concept is still necessary for proper subnet sizing and CIDR calculations.