IPv4 Network & IP Address Calculator
Calculate subnet details instantly from an IPv4 address and subnet mask or CIDR prefix.
Why a network calculator matters
Whether you are a student learning networking, a sysadmin preparing VLANs, or a developer provisioning cloud infrastructure, subnet calculations show up everywhere. An IP address by itself is not enough. You also need the subnet mask (or CIDR prefix) to understand where the network starts, where it ends, and which addresses are usable.
A reliable network and IP address calculator helps you avoid common mistakes that can cause downtime: overlapping subnets, invalid host assignments, and wrong broadcast domains. In practical terms, it gives you confidence before you touch routers, firewalls, DHCP scopes, or security group rules.
What this calculator gives you
- Network address
- Broadcast address
- First usable host and last usable host
- Total addresses and usable host count
- CIDR notation and wildcard mask
- Address class and public/private range hint
- Binary representation of IP and subnet mask
Quick refresher: core subnetting concepts
IP address
IPv4 addresses are 32 bits, usually written as four decimal octets (for example, 10.1.4.22). Each octet ranges from 0 to 255.
Subnet mask
The subnet mask marks which bits belong to the network portion and which bits belong to hosts. A mask of 255.255.255.0 means the first 24 bits are network bits.
CIDR prefix
CIDR is a shorter way to represent the mask. /24 is equivalent to 255.255.255.0. Smaller prefixes (like /16) create larger networks. Larger prefixes (like /28) create smaller networks.
Network and broadcast addresses
The network address identifies the subnet itself. The broadcast address reaches all hosts in that subnet. In most traditional subnets, these two are reserved and not assigned to end devices.
Practical examples
Example 1: Small office LAN
If your host is 192.168.1.50 with /24, the network is 192.168.1.0 and broadcast is 192.168.1.255. Usable range: 192.168.1.1 to 192.168.1.254.
Example 2: Split a /24 into smaller subnets
A /26 creates blocks of 64 addresses each. This is often used to segment departments, labs, guest Wi-Fi, or IoT devices.
- 192.168.1.0/26
- 192.168.1.64/26
- 192.168.1.128/26
- 192.168.1.192/26
Example 3: Point-to-point links
Prefix /31 is special and commonly used for point-to-point links; both addresses can be usable under RFC 3021. Prefix /32 represents a single host route.
Common subnetting mistakes to avoid
- Mixing up subnet mask and wildcard mask (especially in ACLs).
- Assigning the broadcast address to a host device.
- Using overlapping subnets across VLANs or VPN tunnels.
- Assuming every subnet has the same host capacity.
- Forgetting that /31 and /32 have special behavior.
How to use this tool effectively
- Enter the IP address of the host or interface.
- Enter mask as dotted decimal or CIDR prefix.
- Click Calculate.
- Use the computed network details to configure routers, DHCP, ACLs, and firewall rules.
Final thoughts
Subnetting becomes easy when you can instantly verify your assumptions. Use this calculator as a fast validation step while planning or troubleshooting networks. It is especially useful when moving between on-prem infrastructure and cloud VPC/VNet designs where CIDR boundaries matter.