CIDR Calculator

Calculate subnet details from an IP address and CIDR notation.

CIDR (Classless Inter-Domain Routing) notation defines IP address ranges and subnet masks in a compact format like 192.168.1.0/24. Our CIDR calculator computes network address, broadcast address, usable host range, subnet mask, and total number of hosts.

Result

Enter an IP/CIDR to calculate.
In Action

CIDR Calculator in action

Your cloud console asks for a VPC range and your team suggests 10.1.0.0/20. The calculator instantly shows 4,096 addresses — more than your whole region needs — so you right-size to /22 and keep the address plan clean for future expansion.

Frequently Asked Questions

What is CIDR notation?

CIDR notation specifies an IP address and its subnet mask using a prefix length (e.g. /24).

How do I calculate a subnet from CIDR notation?

Enter the CIDR (e.g. 10.0.0.0/24) and the calculator shows network address, broadcast, usable host range, and the number of addresses. No manual binary math required.

What is the difference between /24 and /16 subnets?

A /24 contains 256 addresses (254 usable) and suits a small office. A /16 contains 65,536 addresses and suits a large campus. Smaller CIDR number means bigger network; the calculator shows the exact count for any prefix.

How many usable hosts are in a /30 network?

A /30 has 4 addresses, 2 usable — which is why it is the standard for point-to-point links between routers. The network and broadcast addresses consume the other two.