IP Subnet Calculatorv1.0.0

Calculate network address, broadcast address, CIDR prefix, and usable host range for IPv4 and IPv6 in one place. View class, mask, wildcard, and binary mask for IPv4, and see expanded, compressed, and reverse DNS formats for IPv6. Copy clean, normalized results to speed up network design, change requests, and incident response.

• Generate accurate network, broadcast, and host ranges for any valid IPv4 or IPv6 input.
• Validate firewall rules, ACLs, and security groups by confirming exact CIDR boundaries.
• Plan DHCP scopes and address pools with clear usable host counts and neighbor subnets.
• Create routing summaries and aggregation plans by aligning prefixes to binary boundaries.
• Troubleshoot addressing issues by identifying private, link-local, loopback, multicast, and reserved blocks.

Enter an IP address, choose a subnet mask or prefix length, and run the calculation. Read the summary table to confirm the family, prefix, and total addresses, then review details for copy-ready values.

• Type an address in IP Address such as 192.0.2.10 or 2001:db8::1.
• Select a Subnet Mask for IPv4 or a Prefix Length for IPv6, for example /24 or /64.
• Choose an optional Network Class filter to warn on out-of-class IPv4 octets.
• Press Calculate to generate network address, range, host counts, and neighbor subnets. Press Reset to restore defaults.
• Copy any value for documentation, firewall changes, DHCP configuration, or routing updates.

• Plan subnets for new VLANs, VPCs, or VNets and avoid overlap across environments.
• Verify NAT, VPN, and peering configurations by checking exact CIDR alignment.
• Design IPv6 deployments with /64 for SLAAC and correct reverse DNS zones.
• Prepare change tickets with normalized network, broadcast, and range fields.
• Audit existing networks by classifying addresses as private, public, or reserved.

Example 1: Enter 192.168.1.34 with /26 to produce network 192.168.1.0/26, broadcast 192.168.1.63, and 62 usable hosts. Use this to carve out a small server VLAN.

Example 2: Enter 10.0.8.1 with /20 to produce network 10.0.0.0/20 through 10.0.15.255 with 4094 usable hosts. Use this to size a campus user segment.

Example 3: Enter 2001:db8:abcd::1 with /64 to produce a standard SLAAC subnet and a correct ip6.arpa reverse zone path. Use this to set forward and reverse records for IPv6 services.

What is CIDR? CIDR is the prefix length that states how many leading bits define the network. For example, /24 means 24 network bits and 8 host bits.

Why do /31 and /32 look different? /31 supports point-to-point links with two usable addresses and no broadcast. /32 represents a single host and has no usable range.

Why is /64 common for IPv6? /64 enables Stateless Address Autoconfiguration and keeps host addressing consistent across networks.

Can I list every address? The tool lists small ranges inline and offers a downloadable list for larger subnets to keep the page responsive.

• IPv4 netmask from prefix p: netmask = (2^32 − 1) << (32 − p)
• Network address: IP AND netmask; Wildcard mask: NOT netmask; Broadcast: network OR wildcard
• Usable hosts (IPv4): p = 32 → 0; p = 31 → 2; else 2^(32 − p) − 2
• IPv6 network: keep first p bits, set remaining bits to 0; Reverse DNS: expand, reverse nibbles, append .ip6.arpa