Terms & Privacy Policy

1 Acceptance of Terms

By accessing or using Sleep Calculator at thesleepcalculator.online (the "Service"), you confirm that you have read, understood, and agree to be bound by these Terms of Service and Privacy Policy ("Terms"). If you do not agree with any part of these Terms, you must not use the Service.

These Terms apply to all visitors and users of the Service, regardless of how you access it — via web browser, mobile device, or any other means.

2 Description of Service

Sleep Calculator is a free, web-based tool that calculates recommended bedtimes and wake-up times based on the 90-minute sleep cycle model and a standard 15-minute sleep onset period. The Service is provided entirely free of charge and requires no registration or account creation.

What the Service Does

• Calculates optimal bedtimes based on a desired wake-up time you provide
• Calculates optimal wake-up times if you intend to sleep immediately
• Displays your local time using IP-based timezone detection
• Provides general educational information about sleep science and sleep hygiene

What the Service Does NOT Do

• Provide personalised medical or clinical sleep advice
• Diagnose, treat, or cure any sleep disorder or health condition
• Store your personal sleep data between sessions
• Require account registration or collect personally identifiable information

3 Medical Disclaimer

Individual sleep requirements vary significantly based on age, health conditions, medications, lifestyle factors, and other variables that this tool cannot account for. The 90-minute sleep cycle and 15-minute onset figures used are averages derived from published sleep science literature.

You should always consult a qualified medical professional or sleep specialist if you:

• Experience persistent difficulty falling or staying asleep
• Suffer from excessive daytime sleepiness or fatigue
• Have been diagnosed with or suspect a sleep disorder (such as insomnia, sleep apnoea, narcolepsy, or restless legs syndrome)
• Are taking medications that affect sleep
• Experience significant changes in your sleep patterns

By using this Service, you acknowledge that Sleep Calculator bears no responsibility for any health outcomes resulting from the use of, or reliance on, the information provided.

4 Data We Collect

We are committed to your privacy. Sleep Calculator is designed to collect as little data as possible. Below is a transparent breakdown of what is and is not collected.

Information We Do NOT Collect

• Your name, email address, or any personally identifiable information
• Your sleep schedule, bedtimes, or wake-up time inputs — these are processed locally in your browser and never sent to our servers
• Passwords (no accounts exist)
• Payment information (the Service is free)

Information Automatically Collected

• IP address — used solely for timezone detection to display your local time (see Section 5). Your IP is sent to a third-party geolocation service and is not stored by us.
• Browser type and version — collected anonymously via analytics to improve compatibility
• Pages visited and time on site — collected anonymously via analytics to understand usage patterns
• Device type (mobile, desktop, tablet) — for optimising the user interface
• Referring URL — the page that linked you here, used for analytics only
• General geographic region — country-level only, derived from IP for analytics. We do not collect precise location.

5 Geolocation & IP Data

To display an accurate local time for your location, Sleep Calculator sends your IP address to one or more third-party geolocation APIs. These services return a timezone identifier (e.g., "Europe/London") and city name which are used only to display your local time in the clock widget.

Geolocation APIs We Use

• ip-api.com — primary provider. Their privacy policy is available at ip-api.com
• ipwho.is — secondary fallback provider
• ipapi.co — tertiary fallback provider
• worldtimeapi.org — final fallback provider

These APIs may log your IP address according to their own privacy policies, which we do not control. We only use the timezone and city data returned — we do not store, log, or process your IP address on our servers.

If all API calls fail (e.g., due to network restrictions), the Service falls back to your browser's locally configured timezone. You can disable JavaScript to prevent these API calls, though the clock widget will not function.

6 Cookies & Local Storage

Sleep Calculator uses a minimal approach to cookies and browser storage.

Cookies We Use

• Analytics cookies (e.g., Google Analytics) — used to understand how users interact with the Service, such as pages visited and session duration. These are anonymised and do not identify you personally.
• No session cookies — we do not use login sessions or session-tracking cookies
• No advertising cookies — we do not use third-party advertising or retargeting cookies

Managing Cookies

You can control and delete cookies through your browser settings. Disabling cookies will not affect the core functionality of the sleep calculator, but may affect the accuracy of our anonymous analytics. For more information on managing cookies, visit allaboutcookies.org.

Local Storage

Sleep Calculator does not use browser localStorage or sessionStorage to store any data about you or your usage.

7 Third-Party Services

Sleep Calculator integrates with the following third-party services. Each has its own privacy policy and data practices which we encourage you to review.

Google Analytics

We use Google Analytics to collect anonymous usage statistics. Google Analytics uses cookies to collect data such as pages visited, session duration, and device type. This data is aggregated and anonymous — Google Analytics cannot identify you as an individual. You can opt out by installing the Google Analytics Opt-out Browser Add-on available at tools.google.com/dlpage/gaoptout.

Google Fonts

This website loads fonts from Google Fonts (fonts.googleapis.com). When your browser requests these fonts, Google may collect your IP address and browser information. This is standard practice for web font delivery. See Google's Privacy Policy at policies.google.com/privacy for details.

Geolocation APIs

As described in Section 5, your IP address is sent to geolocation services to determine your timezone. These services operate independently and have their own data retention policies.

8 Intellectual Property

All content on Sleep Calculator — including but not limited to the website design, layout, graphics, text, code, and branding — is the exclusive property of Sleep Calculator and is protected by applicable copyright and intellectual property laws.

• You may not copy, reproduce, distribute, modify, or create derivative works of any part of this Service without prior written consent
• You may share links to the Service freely
• The sleep cycle calculations are based on publicly available scientific research and general knowledge; the specific implementation and presentation are proprietary
• Scraping, automated data extraction, or systematic copying of content from this Service is prohibited

The name "Sleep Calculator", the moon logo, and associated branding elements are trademarks of Sleep Calculator. Unauthorised use is prohibited.

9 Limitation of Liability

Sleep Calculator is provided on an "as is" and "as available" basis without any warranties of any kind, either express or implied, including but not limited to warranties of merchantability, fitness for a particular purpose, or non-infringement.

To the fullest extent permitted by applicable law, Sleep Calculator and its operators shall not be liable for:

• Any indirect, incidental, special, consequential, or punitive damages arising from your use of the Service
• Any errors, inaccuracies, or omissions in the sleep calculations or educational content
• Any health outcomes resulting from reliance on the Service's recommendations
• Any interruption, suspension, or discontinuation of the Service
• Any unauthorised access to or alteration of your transmissions or data
• Any data loss or corruption

In jurisdictions that do not allow exclusion of implied warranties or limitation of liability for incidental or consequential damages, the above limitations may not apply to you.

10 Changes to These Terms

We reserve the right to modify or replace these Terms at any time at our sole discretion. When we make material changes, we will update the "Last Updated" date at the top of this page.

Your continued use of the Service after any changes constitutes your acceptance of the new Terms. If you do not agree to the updated Terms, you must stop using the Service.

We encourage you to review this page periodically. We will not notify users individually of changes unless required by law to do so.

11 Governing Law

These Terms shall be governed by and construed in accordance with applicable laws, without regard to conflict of law provisions. Any disputes arising under or in connection with these Terms shall first be attempted to be resolved informally by contacting us directly.

If you are accessing the Service from the European Union, you have certain rights under the General Data Protection Regulation (GDPR), including the right to access, correct, or delete personal data we hold about you. Since we collect minimal personal data, most GDPR requests can be addressed by simply clearing your browser cookies.

If you are a California resident, you may have additional rights under the California Consumer Privacy Act (CCPA). Please contact us for more information.