CIDR Calculator
Calculate the subnet mask and address counts for a CIDR block.
Calculate
Enter your values below.
Result
Subnet mask
0
Total addresses
0
Usable hosts
0
Formula used
Total addresses = 2^(32 − prefix)
Example: 10.0.0.0/16 → subnet mask 255.255.0.0, 65,536 total addresses.
How to use this calculator
- Enter Base IP address, CIDR prefix (/n).
- Press Calculate to see your result instantly.
FAQ
Frequently asked questions
What does CIDR stand for?
Classless Inter-Domain Routing — a way of allocating IP addresses without fixed class boundaries.
How is the subnet mask derived from the prefix?
The prefix number of leading bits are set to 1, and the rest to 0, then written in dotted-decimal form.
What's the difference between this and the IPv4 Subnet Calculator?
This focuses on the block size (mask and address counts); the Subnet Calculator additionally computes network/broadcast addresses for a specific IP.
What is a /32 prefix?
A single host address, with no additional network bits — the smallest possible block.