CIDR Calc

Subnet mask calculator.

Enter an IP with a dotted mask to calculate prefix length, network, broadcast, and usable host range.

Open mask calculatorFull calculator

Quick checks

  • 255.255.255.0 equals /24.
  • 255.255.0.0 equals /16.
  • 255.255.255.252 equals /30.

Example

IP: 10.0.0.1

Mask: 255.0.0.0

Result

/8, network 10.0.0.0

Tip

Non‑contiguous masks are invalid. CIDR Calc validates masks before converting to prefixes.