IPv4 Subnet Calculator
Enter an IPv4 address and CIDR prefix to calculate network details instantly.
What a Network Calculator Subnet Tool Solves
Subnetting is one of the most practical skills in networking, but doing it manually can be slow and error-prone— especially when you are under time pressure. A network calculator subnet tool quickly converts an IP address and CIDR block into all the important values you need for planning and troubleshooting.
Instead of calculating bit boundaries by hand, this tool gives you network address, broadcast address, host range, subnet mask, wildcard mask, and host capacity in one click. It is useful for IT admins, students, engineers, and anyone preparing for networking certifications.
Subnetting Terms You Should Know
IP Address
An IPv4 address is a 32-bit number usually written in dotted decimal notation, such as 192.168.10.77.
CIDR Prefix
CIDR (Classless Inter-Domain Routing) uses a slash notation like /24 or /27. The prefix tells you how many bits are reserved for the network portion.
Subnet Mask
The subnet mask is the dotted decimal representation of the prefix. For example:
- /24 = 255.255.255.0
- /27 = 255.255.255.224
- /30 = 255.255.255.252
Network and Broadcast
- Network Address: first address in the subnet (identifies the subnet itself).
- Broadcast Address: last address in the subnet (used to send traffic to all hosts in that subnet).
Usable Host Range
In most subnets, usable hosts are all addresses between network and broadcast. Special cases:
- /31: both addresses are usable on point-to-point links.
- /32: a single host route.
How to Use This Subnet Calculator
- Enter an IPv4 address (example: 10.20.30.44).
- Enter a prefix (example: 23).
- Click Calculate Subnet.
- Review the output table and use it in your network design.
The calculator validates your input, catches malformed IP addresses, and provides a clear summary you can copy into documentation.
Worked Example
For 192.168.10.77/27, the results are:
- Subnet mask: 255.255.255.224
- Network address: 192.168.10.64
- Broadcast address: 192.168.10.95
- Usable range: 192.168.10.65 to 192.168.10.94
- Total addresses: 32
- Usable hosts: 30
This tells you exactly which addresses are valid for devices and where the subnet boundaries exist.
Common CIDR Quick Reference
- /16 → 255.255.0.0 → 65,536 total addresses
- /24 → 255.255.255.0 → 256 total addresses
- /25 → 255.255.255.128 → 128 total addresses
- /26 → 255.255.255.192 → 64 total addresses
- /27 → 255.255.255.224 → 32 total addresses
- /28 → 255.255.255.240 → 16 total addresses
- /29 → 255.255.255.248 → 8 total addresses
- /30 → 255.255.255.252 → 4 total addresses
Practical Uses in Real Networks
VLAN Segmentation
You can assign one subnet per VLAN to isolate departments, improve security, and reduce broadcast domains.
Capacity Planning
If your office has 40 devices, a /26 (62 usable hosts) may be a better fit than a /24. Better subnet sizing keeps address usage efficient.
Troubleshooting
If two hosts cannot communicate, a subnet mismatch is often the cause. This calculator helps verify whether each host is in the same network and whether gateway settings are consistent.
Final Thoughts
A good network calculator subnet workflow saves time, reduces mistakes, and makes your network plans easier to explain. Use the tool above whenever you design new segments, audit existing ranges, or validate configurations before deployment.