Formula
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
- IPv4 only. /31 assumes point-to-point use and /32 one host; reserved or public routability is not checked.
Example Calculation
- IPv4 address: 192.168.1.130
- CIDR prefix: 26
192.168.1.130/26 belongs to 192.168.1.128–192.168.1.191, with 64 total addresses.
Method references
Frequently asked questions
How do I use this calculator?
Enter ipv4 address, cidr prefix. The result updates automatically. Use Reset to restore the example values.
What method does it use?
block size=2^(32−prefix); network=floor(address/block) × block.. IPv4 only. /31 assumes point-to-point use and /32 one host; reserved or public routability is not checked.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.