IP Subnet Calculator Online Free — CIDR, Netmask & Subnetting

Calculate subnet mask, network address, broadcast address, and host range from IP and CIDR. Free, no signup required.

IP Address

CIDR

Network192.168.1.0

Broadcast192.168.1.255

Subnet Mask255.255.255.0

Wildcard0.0.0.255

First Host192.168.1.1

Last Host192.168.1.254

Hosts254

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How to Use

Enter an IP address (e.g., 192.168.1.100)
Enter the CIDR prefix length (e.g., /24) or subnet mask
View the calculated network address, broadcast, and host range
Copy any value you need for your network configuration

Common Use Cases

Planning IP address allocation for cloud VPCs
Configuring firewall rules with correct subnet ranges
Studying for network certification exams (CCNA, CompTIA)
Troubleshooting network connectivity issues

Frequently Asked Questions

What is CIDR notation?

CIDR (Classless Inter-Domain Routing) notation like /24 indicates how many bits are used for the network portion of an IP address. /24 means 24 network bits and 8 host bits, allowing 254 usable hosts.

How do I calculate the number of hosts in a subnet?

The formula is 2^(32-prefix) - 2 for IPv4. The subtraction accounts for the network address and broadcast address. A /24 subnet has 2^8 - 2 = 254 usable hosts.

What is the difference between network and broadcast address?

The network address is the first address in a subnet (all host bits 0) and identifies the subnet. The broadcast address is the last (all host bits 1) and sends packets to all hosts in the subnet.