CIDR Calculator

192.168.1.10/24 → network 192.168.1.0/24.

How it works

• Parsed the dotted-quad address and the prefix length.
• Applied the /24 netmask (255.255.255.0) to derive the network address.
• Inverted the netmask to get the wildcard mask and OR-ed it with the network to get the broadcast address.
• Counted usable hosts for the prefix (RFC 3021 for /31 and /32).

network = address AND mask; broadcast = network OR (NOT mask)

• Host bits that were set in the input are reported and the network address is normalised.
• /31 follows RFC 3021 (two usable addresses) and /32 has one usable address.

Methodology

1. Parse the address and prefix with a strict dotted-quad grammar (leading-zero octets are rejected).
2. Derive the netmask from the prefix as a 32-bit unsigned integer (no signed shift overflow).
3. Compute network = address AND mask and broadcast = network OR wildcard.
4. Apply RFC 3021 semantics for /31 and /32 and count the remaining usable addresses.

Usage

1. Enter a CIDR block such as 192.168.1.0/24.
2. Run the calculation.
3. Read or copy the network details.

Examples

These are examples, not current values: they use fixed inputs, while the interactive tool computes live results in your browser.

A /24 office network

{
  "cidr": "192.168.1.10/24"
}

A /8 private block

{
  "cidr": "10.0.0.0/8"
}

An RFC 3021 point-to-point /31

{
  "cidr": "203.0.113.5/31"
}

Limitations

CIDR notation, precisely

CIDR notation appends a prefix length to an IPv4 address: the number of high-order bits that identify the network. Everything below that boundary is host space, and the netmask and wildcard mask are just the two ways of writing that boundary.

The calculator keeps the arithmetic in unsigned 32-bit integers, so boundaries at 128 and above (a /1 through /7) do not overflow the way JavaScript's signed bitwise operators otherwise would.