Formula and practical context.
network = address bitwise-AND prefix maskThe address is parsed as 32 bits for IPv4 or 128 bits for IPv6; prefix length retains the leading network bits.
Formula, variables, and method
network = address bitwise-AND prefix mask. The address is parsed as 32 bits for IPv4 or 128 bits for IPv6; prefix length retains the leading network bits. The result applies a CIDR prefix mask to an IPv4 or IPv6 address and reports the canonical network boundary and address scope. Start by identifying what each entered number represents and whether it is a measured value, a specification, or an assumption. Convert units before combining quantities, preserve full precision through intermediate steps, and round only the displayed result. Parse the address into an unsigned integer, keep the prefix bits with a bit mask, clear host bits, and format the network in its original address family. This sequence makes the output reproducible and helps expose a misplaced unit or decimal point before it affects a decision.
Worked example and independent check
IPv4 address 192.168.1.42 with prefix 24 has network 192.168.1.0, broadcast 192.168.1.255, and 256 total addresses. To check the example independently, write the formula first, substitute the values with their units, and complete one operation at a time. Compare the order of magnitude with a familiar reference rather than accepting a formatted result automatically. Parse the address into an unsigned integer, keep the prefix bits with a bit mask, clear host bits, and format the network in its original address family. If a second method or inverse calculation is available, use it to recover an original input. Small differences from hand calculation should come only from displayed rounding, not from a different definition.
Units and result interpretation
An IPv4 prefix ranges from 0 to 32 bits; an IPv6 prefix ranges from 0 to 128 bits. CIDR is bit-based and has no decimal unit. The result applies a CIDR prefix mask to an IPv4 or IPv6 address and reports the canonical network boundary and address scope. A unit is part of the quantity, not a label added after the arithmetic. Keep decimal and binary prefixes, temperature scales, elapsed-time units, and electrical prefixes explicit. When comparing two scenarios, change one assumption at a time and retain the same unit convention. The result describes only the relationship named by this calculator; it does not automatically establish capacity, safety, compatibility, quality, or compliance.
Validation and boundary cases
Every IPv4 octet must be decimal 0–255. IPv6 accepts valid compressed hexadecimal notation but rejects multiple double-colon contractions and zone identifiers. Blank values, malformed text, non-finite numbers, impossible ranges, zero divisors, and unsupported combinations receive an explicit message rather than a silent fallback. Boundary values are checked before the formula runs. If an input comes from a specification sheet, weather report, network plan, or measurement instrument, confirm its definition and precision. A syntactically valid value can still be unsuitable for the real situation, so inspect the assumptions alongside the result.
Assumptions, privacy, and practical limits
The calculator describes address mathematics only; routing policy, delegated prefixes, DHCP reservations, firewall behavior, and provider assignments are external. Address parsing happens locally. No entered address is transmitted or stored. Use the result as a transparent estimate or transformation, keep the source values with any saved result, and consult the linked authoritative material for definitions and applicability. For safety-critical, health-adjacent, security, network, chemical, or electrical work, verify the result with current standards, official warnings, qualified professionals, and appropriate test equipment.
Check assumptions and sources.
The calculator describes address mathematics only; routing policy, delegated prefixes, DHCP reservations, firewall behavior, and provider assignments are external.
Common questions.
What does the IP Subnet Calculator do?
Validate an IPv4 or IPv6 address and calculate its CIDR network boundary and scope.
How can I check the result?
Parse the address into an unsigned integer, keep the prefix bits with a bit mask, clear host bits, and format the network in its original address family.
Which units and assumptions matter?
An IPv4 prefix ranges from 0 to 32 bits; an IPv6 prefix ranges from 0 to 128 bits. CIDR is bit-based and has no decimal unit. The calculator describes address mathematics only; routing policy, delegated prefixes, DHCP reservations, firewall behavior, and provider assignments are external.
Are the entered values sent or stored?
Address parsing happens locally. No entered address is transmitted or stored.