CIDR Calculator
Calculate CIDR blocks and address ranges.
Calculate CIDR blocks and address ranges.
CIDR calculation
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Tool guide
Free Online CIDR Calculator
Calculate an IPv4 CIDR block from an address and prefix, including its normalized network, broadcast address, subnet mask, wildcard mask, usable range, and address counts. Host bits are normalized automatically during the browser-side calculation.
Steps
How it works
- Enter an IPv4 address in CIDR notation, such as 192.168.1.42/24.
- Run the CIDR calculation in your browser.
- Review the normalized block, masks, range, and counts.
- Copy or download the calculation summary.
Highlights
Key features
- Accepts IPv4 CIDR prefixes from /0 through /32.
- Normalizes host bits to calculate the network boundary.
- Reports subnet and wildcard masks.
- Calculates network and broadcast addresses.
- Shows first and last usable addresses plus total and usable counts.
Use cases
Common uses
- Normalize an IPv4 address and prefix to its CIDR block.
- Check the start and end boundaries of an IPv4 subnet.
- Translate a prefix length into subnet and wildcard masks.
- Estimate the number of addresses available in a block.
Notes
Limitations to know
- This version supports IPv4 CIDR blocks only.
- It does not split a block into smaller subnets or aggregate multiple blocks.
- For /31 and /32, all addresses are reported as usable rather than subtracting traditional reserved endpoints.
- The output does not configure routing, firewalls, or network devices.
- No geolocation, ownership lookup, reachability test, or live network request is performed.
FAQ
Frequently asked questions
What does a prefix such as /24 mean?
It means the first 24 bits identify the network and the remaining 8 bits identify addresses within that IPv4 block.
Does the calculator normalize host bits?
Yes. An input such as 192.168.1.42/24 is calculated from the normalized network address 192.168.1.0.
Is IPv6 supported?
No. The current calculator accepts IPv4 CIDR notation only.
Are network and broadcast addresses included in the total?
Yes. Total addresses cover the entire CIDR block, while the usable count normally subtracts those two endpoints for prefixes below /31.
Can it split one CIDR block into smaller subnets?
No. Subnet splitting and CIDR aggregation are not implemented.