Subnet · IP Calculators
Subnetting, CIDR, masks and IP address conversion — calculators for network design and study.
How to choose a tool
Use the subnet calculator when you know an IP and prefix and need network, broadcast, and host ranges together. Use CIDR-to-range for endpoints and range-to-CIDR for the smallest CIDR blocks covering a continuous range. Use subnet membership for one address, netmask validation for mask syntax, and binary, integer, or IPv6 expansion tools only to change representation.
For example, 192.168.10.0/24 spans 256 IPv4 addresses; a typical LAN plans hosts after reserving network and broadcast addresses. If starting from device count, find a prefix from required hosts, then verify endpoints and spare addresses before deployment. Do not confuse IPv6 text expansion or IPv4-mapped notation with IPv6 routing-prefix calculation.
How to verify the result
First remove stray spaces, ensure each IPv4 octet is 0–255, and keep prefix length within its address family. After calculation, confirm the original IP lies in the range, mask 1-bits are contiguous, and split CIDRs neither overlap nor leave gaps. Sorting ranges and comparing first and last addresses also reveals list-entry mistakes.
These calculations interpret address numbers and prefix rules; they do not inspect or change router routes, VLANs, firewalls, or DHCP reservations. Normal host rules may not apply to /31, /32, and special-use addresses. Before production changes, back up device settings and the address plan, then verify results against vendor documentation and the real routing table.