📐 CIDR Calculator

Enter an IP address and CIDR prefix to see the full network breakdown, plus a complete CIDR-to-subnet-mask reference table below.

Input

Results

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Prefix

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Subnet Mask

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Network

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Broadcast

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First Address

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Last Address

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Total Addresses

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Usable Hosts

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Wildcard Mask

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Binary

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CIDR Reference Table

CIDR	Subnet Mask	Total Addresses	Usable Hosts

How It Works

CIDR (Classless Inter-Domain Routing) notation expresses a subnet mask as a prefix length — the number of leading 1 bits. /24 means the first 24 bits are network bits, equivalent to a 255.255.255.0 mask. This tool converts the prefix to a full mask and calculates the resulting network boundaries.

Examples & Common Use Cases

10.10.10.15/20 → network 10.10.0.0, 4094 usable hosts.
172.16.5.1/16 → a full Class B–sized block, 65,534 usable hosts.
Use the reference table to quickly recall how many hosts a given prefix provides without doing the math by hand.