Terms & conditions.

These terms govern your use of IP CIDR Calculator at ipcidrcalculator.com ("the site"). By using the site you accept them. If you do not accept them, please do not use the site. They took effect on25 August 2026.

1. What the site is

The site provides free, browser-based calculators and reference material for IP addressing and subnetting. It requires no account, no payment and no registration, and all calculations run locally in your browser as described in the privacy policy.

2. No warranty on results

The calculators and reference tables are provided "as is" and "as available", without warranty of any kind, express or implied, including any implied warranty of merchantability, fitness for a particular purpose, accuracy or non-infringement.

Considerable care goes into the arithmetic — it is generated by a single tested module rather than transcribed by hand — but no guarantee is given that every output is correct, complete or current, that the site will be available without interruption, or that it is free of errors. Nothing here is professional, legal or compliance advice.

Verify before you deploy. Address plans, firewall rules, routing entries and allow-lists derived from this site should be checked against your own equipment and against the relevant specification before they are put into production. You are solely responsible for the configurations you build and for any consequence of them.

3. Limitation of liability

To the fullest extent permitted by law, the operator of the site shall not be liable for any indirect, incidental, special, consequential or punitive damages, nor for any loss of profits, revenue, data, goodwill, service availability or business, arising out of or in connection with your use of — or inability to use — the site, whether the claim is based in contract, tort, negligence, strict liability or otherwise, and even if the possibility of such damage was known.

Because the site is supplied free of charge, the total aggregate liability for all claims relating to it is limited to zero. Nothing in these terms excludes or limits liability that cannot lawfully be excluded or limited, such as liability for fraud, for fraudulent misrepresentation, or for death or personal injury caused by negligence.

4. Acceptable use

You may use the site for any lawful purpose, personal or commercial. You may not:

• use it to plan, assist or conceal unlawful activity, including unauthorised access to any network you are not permitted to test;
• attempt to disrupt or degrade the site or its hosting, including by automated requests at a volume that interferes with other users;
• scrape or republish the site's content wholesale so as to present it as your own, or otherwise pass the tools off as your work;
• misrepresent the site's output as a certified, audited or authoritative source; or
• remove, obscure or alter any attribution or notice on the site.

Occasional automated access is not objected to. Sustained scraping is — the pages are static and small, and mirroring them serves nobody.

5. Intellectual property

The design, layout, written explanations and source code of the site are owned by its operator and protected by copyright. You may use the calculators freely and quote short passages with attribution and a link. Reproducing substantial portions of the written material, or redistributing the site as a whole, needs permission first.

The underlying facts are not owned by anyone: prefix arithmetic, subnet masks, host counts and the contents of the RFCs are public technical knowledge, and nothing here claims otherwise. CIDR, IPv4 and IPv6 are defined by the IETF, and the relevant RFCs are linked throughout for that reason.

6. Third-party links

The site links to external material such as RFCs and registry documentation. Those resources are not under the operator's control, and no responsibility is taken for their content, availability or accuracy.

7. Availability and changes to the site

The site may be modified, suspended or withdrawn at any time without notice. Tools may be added, changed or removed, and URLs may change. No commitment is made to maintain any particular feature, output format or address indefinitely.

8. Changes to these terms

These terms may be revised. The current version is always the one published on this page, with its effective date shown at the top. Continued use of the site after a revision means you accept it, so it is worth re-reading this page if you rely on the tools materially.

9. Severability

If any provision of these terms is found to be unenforceable, that provision is to be limited or severed to the minimum extent necessary, and the remaining provisions continue in full force.

10. Contact

Questions about these terms, and any permission or takedown request, can be sent to hello@ipcidrcalculator.com. Reporting an error in a calculation is always welcome; the contact page explains what to include.