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CIDR / Subnet Calculator

Calculate network range, broadcast, and host counts from CIDR notation.

Runs locally in your browser. Your input is not uploaded or stored. You can verify this in your browser’s network panel.

What does this tool solve?

CIDR notation writes a network as an address plus a prefix length: 192.168.1.0/24 means the 256 addresses from 192.168.1.0 to 192.168.1.255. Enter any address in the block — the calculator normalizes it to the network and shows mask, range, and host counts.

What examples should you start with?

A /24

Input

192.168.1.0/24

Output

Network 192.168.1.0 · Broadcast 192.168.1.255 · 254 usable hosts

A point-to-point /31

Input

10.0.0.0/31

Output

Two usable addresses (10.0.0.0, 10.0.0.1) — no broadcast, per RFC 3021

A single host /32

Input

203.0.113.7/32

Output

Exactly one address: 203.0.113.7

How does it work?

The prefix length says how many leading bits identify the network; the rest identify hosts. The subnet mask is that many 1-bits — /24 is 255.255.255.0.

Network address = address AND mask; broadcast = network OR the inverted mask. All arithmetic is done on 32-bit integers, locally.

What are the edge cases and limits?

  • /31 links have no network or broadcast address — both addresses are usable (RFC 3021).
  • /0 means the entire IPv4 space: 0.0.0.0–255.255.255.255.
  • Typing a host address like 192.168.1.55/24 is fine; host bits are masked off to find the network.
  • IPv6 uses the same idea with 128 bits but is not covered by this calculator.

Technical reference

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