Use this free network mask calculator to find subnet details from an IPv4 address and CIDR prefix (or subnet mask). It computes network address, broadcast address, host range, wildcard mask, and host capacity instantly.
What Is a Network Mask Calculator?
A network mask calculator is a practical tool for converting between IPv4 subnet notation and the real values that matter when you configure routers, firewalls, servers, and switches. Given an IP address and either a CIDR value (like /24) or a subnet mask (like 255.255.255.0), the calculator tells you exactly where the network starts and ends.
In short, it answers questions like:
- What is the network address?
- What is the broadcast address?
- How many host addresses are available?
- What are the first and last usable IPs?
Subnet Mask vs CIDR Prefix
Dotted-Decimal Mask
The traditional mask format uses four octets, such as 255.255.255.0. This shows which bits belong to the network (1s) and which belong to hosts (0s).
CIDR Notation
CIDR expresses the same thing in slash notation, like /24. The number after the slash is simply how many bits are “network bits.” For example:
- /8 = 255.0.0.0
- /16 = 255.255.0.0
- /24 = 255.255.255.0
- /30 = 255.255.255.252
How to Use This Network Mask Calculator
- Enter an IPv4 address (for example, 10.20.30.40).
- Enter a CIDR prefix (such as 26) or type a subnet mask.
- Click Calculate.
- Read the network details instantly in the results panel.
This is useful for subnetting, troubleshooting overlap issues, checking host capacity, and validating address plans before deployment.
Example Calculation
Input: 192.168.10.57/26
A /26 subnet means 64 total addresses per subnet. The calculator will identify the containing subnet and output:
- Network address: 192.168.10.0
- Broadcast address: 192.168.10.63
- Usable host range: 192.168.10.1 to 192.168.10.62
- Usable hosts: 62
Common Prefixes and Host Capacity
- /24 → 256 total addresses, 254 usable hosts
- /25 → 128 total addresses, 126 usable hosts
- /26 → 64 total addresses, 62 usable hosts
- /27 → 32 total addresses, 30 usable hosts
- /28 → 16 total addresses, 14 usable hosts
- /29 → 8 total addresses, 6 usable hosts
- /30 → 4 total addresses, 2 usable hosts
Common Subnetting Mistakes to Avoid
- Using non-contiguous subnet masks (invalid for normal IPv4 subnetting).
- Assigning the network address or broadcast address to hosts.
- Assuming every subnet has the same host capacity without checking prefix length.
- Mixing up wildcard masks and subnet masks in ACL configurations.
Why This Matters for Real Networks
Subnet design affects scalability, routing simplicity, performance domains, and security boundaries. A quick calculator reduces human error and speeds up planning tasks for VLAN design, cloud VPC ranges, VPN tunnels, and enterprise segmentation.
Whether you are studying for Network+, CCNA, or managing production infrastructure, a reliable network mask calculator saves time and helps prevent costly address conflicts.