How much caffeine is safe per day?

The FDA recommends that healthy adults consume no more than 400 mg of caffeine per day — roughly 4 cups of brewed coffee. Pregnant or breastfeeding women should limit intake to 200 mg, and adolescents to 100 mg. Children under 12 should avoid caffeine entirely.

What is the half-life of caffeine?

Caffeine has an average half-life of about 5 hours in healthy adults, meaning half of the caffeine you consume is still in your body 5 hours later. Half-life varies from 3 to 7 hours based on genetics, pregnancy, smoking, and medications.

How long before bed should I stop drinking caffeine?

Because caffeine has a 5-hour half-life, you should stop consuming it at least 8 hours before bedtime. For most people, that means no coffee or energy drinks after 2 PM if you go to bed at 10 PM.

How much caffeine is in a cup of coffee?

An 8 oz cup of brewed coffee contains about 95 mg of caffeine. A single espresso shot has about 63 mg, and an instant coffee has about 62 mg. Decaf still contains about 2 mg per cup.

How much caffeine is in an energy drink?

An 8.4 oz Red Bull has about 80 mg of caffeine. A 16 oz Monster or Rockstar has about 160 mg. High-performance energy drinks like Bang can contain up to 300 mg per 16 oz can.

Can caffeine affect sleep?

Yes. Caffeine blocks adenosine receptors in the brain, which delays the onset of sleep and reduces deep sleep quality. To protect sleep, keep caffeine below 50 mg in the 8 hours before bedtime.

Privacy Policy

The short version: we don't collect personal data, we don't use tracking cookies, and we don't store your calculator inputs. Everything runs in your browser.

Last updated: October 19, 2026

1. Who we are

Caffeine Math (the "Site") is operated as a free, independent resource. We do not have a corporate parent, and we do not share data with any third party. If you have questions about this policy, please contact us.

2. What we do NOT collect

We do not collect or store any of the following:

Your name, email, phone number, or any other personal identifier
Your IP address is not logged by our application servers (it may be logged transiently by our hosting provider for security/DDoS protection, but is not retained or analyzed)
The beverages you add to the calculator, your body weight, your bedtime, or any other inputs you enter into our tools — all calculations happen entirely in your browser and are never sent to our servers
Your browsing history on other sites
Any form of account or login information — we have no accounts

3. What we DO collect (anonymized)

We use a privacy-respecting analytics service to understand aggregate traffic patterns — which pages are visited, which countries visitors come from, and which referrers send traffic. This data is anonymized, aggregated, and cannot be linked back to you individually.

Page URLs visited (e.g., /calculator, /half-life)
Country (derived from IP, but the IP itself is not stored)
Referrer URL (the page you came from)
Device type (mobile, tablet, desktop) and browser family
Aggregate session duration (rounded to the nearest 10 seconds)

We use this aggregate data only to understand which tools are useful and where to improve the site. We do not use it to build profiles, target ads, or share with third parties.

4. Cookies

We use a single first-party cookie to remember your light/dark theme preference. This cookie is set only when you click the theme toggle, is stored on your device, and is never sent to our servers.

We do not use any of the following:

Third-party advertising cookies (Google AdSense, Facebook Pixel, etc.)
Cross-site tracking cookies
Analytics cookies that store a persistent user ID (we use privacy-respecting analytics that hash the IP and discard it)
Remarketing or retargeting pixels of any kind

Because we don't use tracking cookies, this site is compliant with the EU ePrivacy Directive (cookie law) and does not require a cookie banner.

5. GDPR (European Economic Area & UK)

Under the General Data Protection Regulation (GDPR), you have the following rights regarding your personal data:

Right of access — request a copy of any personal data we hold about you
Right to rectification — request correction of inaccurate data
Right to erasure — request deletion of your personal data
Right to object — object to processing of your data
Right to data portability — receive your data in a structured format

Because we do not collect personal data, there is typically nothing to access, rectify, or erase. If you believe we hold personal data about you (for example, if you emailed us), you may exercise any of these rights by contacting us. We respond to all verified requests within 30 days.

Our legal basis for processing aggregate analytics data is legitimate interest (Article 6(1)(f) GDPR) — we use it to understand how the site is used and improve it, and this processing does not impact your rights or freedoms.

6. CCPA (California)

Under the California Consumer Privacy Act (CCPA), California residents have the right to:

Know what personal information is collected about them
Know whether their personal information is sold or disclosed
Request deletion of their personal information
Opt out of the sale of their personal information
Not be discriminated against for exercising these rights

We do not sell personal information. We do not collect personal information about California residents beyond the anonymized analytics described in Section 3. If you have a CCPA request, please contact us.

7. Children's privacy

Our site is intended for general audiences and is not directed at children under 13. We do not knowingly collect personal information from children under 13. If you believe a child has provided us with personal information, please contact us and we will delete it immediately.

8. Third-party links

Our site contains links to external sites (e.g., USDA FoodData Central, FDA.gov, scientific journals). We are not responsible for the privacy practices of these external sites. We recommend reviewing their privacy policies before providing them with any personal information.

9. Data security

Because we don't store personal data, there is no personal data to breach. Our hosting provider (a major cloud platform) handles standard DDoS protection and TLS encryption in transit. All calculator inputs are processed entirely client-side in your browser using JavaScript, and are never transmitted to our servers.

10. Changes to this policy

We may update this policy from time to time. When we do, we'll update the "Last updated" date at the top of this page. If we make material changes — for example, if we ever begin collecting personal data — we'll update this page and add a prominent notice on the home page at least 30 days before the change takes effect.

11. Contact

If you have questions about this privacy policy or want to exercise any of your data rights, please visit our contact page. We aim to respond to all legitimate inquiries within 7 days.