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CIDR Calculator (Subnet Calculator)

Enter a CIDR block or an IP and mask to see the details instantly.

Your text and files never leave your browser — nothing is sent to a server.

Results
    Binary view

    The highlighted bits are the network part; the rest is the host part.

    How to use

    1. Enter a CIDR such as 192.168.1.0/24, or an IP and mask separated by a space, such as 192.168.1.10 255.255.255.0. A bare IP is treated as a single address (/32).
    2. The network address, broadcast, first and last usable IPs and host count appear right away. “Copy” grabs all the results as text.
    3. For IPv4, the binary view on the right color-codes the network and host bits.
    4. Enter an IPv6 block such as 2001:db8::/48 to get its address range and the number of /64 subnets.

    FAQ

    Why does a /24 only have 254 usable IPs?

    A /24 has 256 addresses, but the first (network address) and last (broadcast) cannot be assigned to devices. The exceptions are /31, where both addresses are usable on point-to-point links, and /32, which is a single address.

    What is a wildcard mask used for?

    It is the inverse of the subnet mask and is used to specify ranges in Cisco ACLs and OSPF configuration. The wildcard for a /24 is 0.0.0.255.

    Does IPv6 have a broadcast address?

    No — IPv6 uses multicast instead. That is why this tool shows only the first and last address and the total count for IPv6 blocks.

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