What is a CIDR calculator used for?

A CIDR calculator converts between CIDR notation (like 192.168.1.0/24) and IP address ranges, showing the network address, broadcast address, usable host range, and total number of addresses.

Does it support IPv6?

Yes. The calculator handles both IPv4 and IPv6 CIDR notation, including full and abbreviated IPv6 addresses.

Can I check if an IP is in a subnet?

Yes. Enter a CIDR block and an IP address to check whether the IP falls within that subnet range.

What is the difference between /24 and /32?

A /24 subnet contains 256 addresses (254 usable hosts), while /32 represents a single host address. Each bit added to the prefix length halves the number of available addresses.

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CIDR / Subnet Calculator

CIDR / Subnet Calculator

Calculate subnets, split networks, and visualize IP address allocation

🔢 Network Calculator

CIDR Notation

Network Information

Binary Representation

Address Space Visualization

✂️ Subnet Splitter

Split your network into smaller subnets

Number of Subnets

🌐 Supernet Calculator

Combine multiple networks into a supernet

Networks (one per line)

🔄 IP Range to CIDR

Convert IP range to CIDR notation

Start IP

End IP

📋 CIDR Reference Table

CIDR	Subnet Mask	Total Addresses	Usable Hosts	Common Use Case
`/8`	`255.0.0.0`	16,777,216	16,777,214	Class A networks
`/16`	`255.255.0.0`	65,536	65,534	Large enterprise
`/20`	`255.255.240.0`	4,096	4,094	AWS default VPC
`/24`	`255.255.255.0`	256	254	Home/small office
`/25`	`255.255.255.128`	128	126	Small department
`/26`	`255.255.255.192`	64	62	Point-to-point
`/27`	`255.255.255.224`	32	30	Small subnet
`/28`	`255.255.255.240`	16	14	Tiny network
`/30`	`255.255.255.252`	4	2	Point-to-point link
`/31`	`255.255.255.254`	2	2	RFC 3021 P2P
`/32`	`255.255.255.255`	1	1	Host route

❓ Frequently Asked Questions

What is CIDR notation?

CIDR (Classless Inter-Domain Routing) notation is a method for describing IP networks. It uses a format like 192.168.1.0/24, where the number after the slash indicates how many bits are used for the network portion. The remaining bits are for host addresses.

How do I calculate the number of hosts in a subnet?

Subtract the network bits from 32 (for IPv4) or 128 (for IPv6), then calculate 2^(host bits) – 2. The -2 accounts for the network address and broadcast address, which cannot be assigned to hosts. For example, /24 has 8 host bits: 2^8 – 2 = 254 usable hosts.

What’s the difference between /24 and /25?

A /24 network has 24 network bits and 8 host bits, providing 256 total addresses (254 usable for hosts). A /25 network has 25 network bits and 7 host bits, providing 128 total addresses (126 usable for hosts). The /25 effectively splits a /24 network into two equal parts.

What are private IP address ranges?

Private IP ranges defined in RFC 1918 are: 10.0.0.0/8 (10.0.0.0 – 10.255.255.255), 172.16.0.0/12 (172.16.0.0 – 172.31.255.255), and 192.168.0.0/16 (192.168.0.0 – 192.168.255.255). These addresses are not routed on the public Internet and are used for internal networks.

How do I subnet a /24 network?

To subnet a /24 network, borrow bits from the host portion. For 2 subnets, use /25 (126 hosts each). For 4 subnets, use /26 (62 hosts each). For 8 subnets, use /27 (30 hosts each). Each additional bit borrowed doubles the number of subnets but halves the number of hosts per subnet.

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