CIDR Subnet Calculator
Get the network and broadcast address instantly from an IP and CIDR prefix
Enter an IPv4 address and a CIDR prefix (/0 to /32) to instantly get the network address, broadcast address, subnet mask, usable IP range, and host count. It's built for network design, server firewall rules, and carving up cloud VPC subnets. Everything is calculated on the spot in your browser, so the IP information you enter is never sent to a server.
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🔒 Everything runs 100% in your browser. Your files and input are never uploaded to any server.
How to use
- Enter the IPv4 address you want to calculate in the IP address field (for example, 192.168.1.1)
- Enter a subnet value between 0 and 32 in the CIDR prefix field (for example, 24)
- The network address, broadcast address, and subnet mask appear automatically
- Check the usable IP range and the host count (usable versus total)
FAQ
- How are /31 and /32 subnets handled?
- A /32 has exactly one usable host (itself), and a /31 is calculated with both IPs usable, since it has no separate network and broadcast addresses. For ordinary subnets (/0 to /30), usable hosts are everything except the network and broadcast addresses.
- Does it support IPv6?
- Not currently — only IPv4 addresses (for example, 192.168.1.1). Entering an IPv6 address will be flagged as invalid input.
- Is the IP information I enter saved or transmitted?
- No. Everything runs inside your browser and nothing is sent to or stored on a server.