IP/CIDR calculator
Calculate IPv4 or IPv6 network boundaries and address counts. IPv4 /31 uses point-to-point semantics; /32 is a single address. No network connections are made. The network prefix identifies the whole block, even when the entered address is a host inside it. Counts remain exact and IPv6 addresses are compressed for readability.
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Your inputs
Edit the example inputs to match your task. Results update as you edit.
Calculations run in your browser. Inputs are not saved or sent to analytics.
How it works
- → Network address; Last address
- Addresses are converted to integers to compute the network boundary and final address exactly, including IPv6 counts. IPv4 /31 and /32 counts follow their special host conventions.
Input and formula key
Your result
Complete the inputs to see your result.
Sources
- IETF RFC 4632 — CIDR notation and address blocksSources reviewed: 2026-11-06
- IETF RFC 3021 — IPv4 /31 point-to-point linksSources reviewed: 2026-11-06
- IETF RFC 4291 — IPv6 addressing, sections 2.2 and 2.3Sources reviewed: 2026-11-06
- IETF RFC 5952 — canonical IPv6 text representationSources reviewed: 2026-11-06
Assumptions and limitations
No DNS lookup, routing test or network scan is performed. Calculated host counts do not prove which addresses are configured, reachable or usable in your network. IPv6 has no IPv4-style broadcast address.
How to use this tool
Set up the inputs
Enter an IPv4 or IPv6 address with its slash prefix, then read the normalized network, last address and exact count. For IPv4, also check the mask and usable endpoints.
Understand the result
The network prefix identifies the whole block, even when the entered address is a host inside it. Counts remain exact and IPv6 addresses are compressed for readability.
Worked examples
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Find the usable range of a private subnet
192.168.1.10/24 → 192.168.1.0/24; 192.168.1.255; 256 − 2 = 254.
Frequently asked questions
What are the limits of this tool?
No DNS lookup, routing test or network scan is performed. Calculated host counts do not prove which addresses are configured, reachable or usable in your network. IPv6 has no IPv4-style broadcast address.
How does the calculation work?
Addresses are converted to integers to compute the network boundary and final address exactly, including IPv6 counts. IPv4 /31 and /32 counts follow their special host conventions.
Processing and privacy
The calculation or transformation runs in your browser. The tool does not send its input values or generated output to an application server. Loading a page still makes infrastructure requests; optional analytics and Google consent messages have separate controls.
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Help and feedback
Consult the linked sources for definitions and reference data. Contact Support if you have a question or notice a problem.
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