Type an IPv4 address into the first field and a CIDR prefix length (0-32) into the second. The network address, broadcast address, subnet mask, wildcard mask, usable host range and total/usable host counts below update on every keystroke - nothing is uploaded and no calculation waits on a server round-trip.
Subnet Calculator (IPv4 CIDR)
Enter an IPv4 address and a CIDR prefix length to get the network address, broadcast address, subnet mask, wildcard mask and usable host range instantly. The math runs in your browser - no upload, no account, and nothing you type leaves the page.
Use this when you are planning IP address ranges, checking whether two hosts sit in the same subnet, or verifying a CIDR block before you configure a router, firewall, or cloud VPC. Change either the address or the prefix and every value updates as you type.
Point-to-point /31 links (RFC 3021) and single-host /32 routes are handled correctly - the tool does not reserve a network or broadcast address for those two prefix lengths, matching how real routers treat them.
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Frequently Asked Questions
What does the subnet calculator do?
It computes the network address, broadcast address, subnet mask, wildcard mask and usable host range for an IPv4 address and CIDR prefix length (0-32), entirely in your browser.
When should I use a subnet calculator?
Use it when you are planning IP address ranges, checking whether two addresses fall in the same subnet, or verifying a CIDR block before configuring a router, firewall, or cloud VPC.
How are /31 and /32 prefixes handled?
Point-to-point /31 links (RFC 3021) and single-host /32 routes do not reserve a separate network or broadcast address, so every address in the range shows as usable - matching how real routers treat them.