What is a CIDR notation?

CIDR (Classless Inter-Domain Routing) notation specifies an IP address followed by a slash and the number of bits in the subnet mask (e.g. 10.0.0.0/16).

Updated: August 2026 • Verified v1.2

IPv4 Subnet Mask & CIDR Prefix Calculator

Internet & NetworkNetwork

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Network = IP & Mask; Broadcast = Network | ~Mask; Usable = 2^(32-CIDR) - 2

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Understanding Your Results

Calculates network address, broadcast address, first usable IP, last usable IP, total usable hosts, subnet mask (e.g. 255.255.255.0), and wildcard mask.

Practical Guidance & Next Steps

A /24 subnet provides 254 usable host addresses; a /16 provides 65,534 usable addresses.

What is this?

A networking utility that calculates IPv4 subnet allocations and host address ranges.

How does it work?

1. Enter an IPv4 address (e.g. 192.168.1.15). 2. Select CIDR prefix size (e.g. /24 for 255.255.255.0). 3. View exact Network IP, Broadcast IP, Usable Host Range, and Total Host Capacity.

Why use it?

Eliminates binary calculation errors when configuring AWS VPCs, Azure VNets, and local routers.

Technical Scope & Calculation Limitations

Calculates standard IPv4 32-bit subnets (/8 to /30).

Frequently Asked Questions

A /24 subnet has 256 total IP addresses, of which 254 are usable for host devices (the first is the Network address and the last is the Broadcast address).

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