Privacy Policy

1 What data we collect

Your email address — only if you sign up for our newsletter

If you choose to subscribe to our newsletter, we collect your email address and nothing else. We don't ask for your name, location, age, or any other personal information. Signing up is completely optional.

Calculator inputs — processed entirely in your browser

Every calculator on this site (sleep timing, chronotype quiz, caffeine cutoff, sleep debt tracker, and any future tools) runs 100% client-side. When you enter a bedtime, a wake-up goal, or answers to quiz questions, that data is computed locally in your browser and is never sent to our servers. We have no idea what you typed. Once you close the tab, it's gone.

Basic analytics data

We use Google Analytics 4 to understand how people use the site — which calculators are popular, how visitors find us, and whether the site is working correctly. Google Analytics collects anonymized usage data including approximate location (country/region level), device type, browser, and pages visited. This data does not identify you personally. See Section 4 for details.

2 How we use your data

If you subscribe to our newsletter, we use your email address for one thing: sending you the newsletter. That's it.

• We send occasional emails about new calculators, sleep science content, and site updates.
• We do not send promotional emails for third-party products.
• We do not use your email for advertising or ad targeting of any kind.
• We do not share your email with any other business or individual.
• We do not profile you or build any kind of user record.

Analytics data is used solely to understand how the site is being used so we can improve it — for example, identifying which calculators are confusing, which pages load slowly, or whether a mobile layout is broken.

3 Cookies and analytics

Google Analytics 4

We currently use Google Analytics 4 (GA4) to collect anonymized usage statistics. GA4 sets cookies in your browser to track sessions and measure site behavior over time. These cookies do not personally identify you.

GA4 data is processed by Google and subject to Google's Privacy Policy. We have configured GA4 with IP anonymization enabled and do not use any advertising or remarketing features.

Opting out of analytics

You can opt out of Google Analytics tracking across all sites by installing the official Google Analytics Opt-out Browser Add-on. Most modern browsers also let you block third-party cookies or enable "Do Not Track" signals.

No other tracking cookies

We don't use advertising cookies, social media tracking pixels, or any other third-party cookies beyond the analytics described above. No cookies are used to store or transmit your calculator inputs — that data stays in your browser's memory and is never persisted.

4 Third-party services

We work with a small number of third-party services to operate the site. Each one has its own privacy policy, and we only share the minimum data necessary for the service to function.

We do not sell data to any third party, full stop. We do not participate in any data brokerage, advertising network, or cross-site tracking scheme.

5 Data retention

Newsletter emails

We keep your email address for as long as you remain subscribed. Every newsletter email we send includes an unsubscribe link. The moment you click it, your email is removed from our list and deleted from our newsletter provider's database. We do not retain it in any other system, archive, or backup after deletion is requested.

Analytics data

Google Analytics retains aggregated, anonymized usage data for up to 14 months by default. After that period, it is automatically deleted from Google's systems. Since this data is not personally identifiable, it cannot be tied back to you.

Calculator inputs

We have no data to retain. Calculator inputs are never sent to us and exist only in your browser's memory during your session.

6 Children's privacy

The Sleep Math is not directed at children under the age of 13 and we do not knowingly collect personal information from anyone under 13. Sleep science content on this site is written for adults. If you are a parent or guardian and believe your child has provided us with an email address without your consent, please contact us at hello@thesleepmath.com and we will delete it promptly.

7 Your rights

Regardless of where you live, we believe you should have control over your personal data. Here's what you can do:

• Unsubscribe anytime. Every newsletter includes a one-click unsubscribe link. No confirmation email, no dark patterns.
• Request access. You can ask us what data we hold about you. Because we only store email addresses (for subscribers), the answer is usually very simple.
• Request deletion. You can ask us to delete your email address at any time — even if you'd prefer not to use the newsletter's unsubscribe link.
• Opt out of analytics. Use the Google Analytics opt-out add-on or configure your browser to block cookies from google-analytics.com.
• Portability. If you want a copy of the data we hold on you in a machine-readable format, just ask.

To exercise any of these rights, email us at hello@thesleepmath.com. We'll respond within 7 business days. We won't ask you to jump through hoops or fill out lengthy forms.

If you're in the European Union or UK, you also have rights under the GDPR / UK GDPR including the right to lodge a complaint with your local data protection authority. We'd prefer to resolve any concerns directly, but that right is always available to you.

8 Changes to this policy

If we ever change how we collect or use data in a meaningful way, we'll update this page and revise the "Last updated" date at the top. If the changes are significant — for example, if we ever started using advertising — we would notify newsletter subscribers directly by email before the changes took effect.

Minor changes like fixing a typo or clarifying existing language won't require a notification.