Free Caffeine Calculator (+ Guide)
A free caffeine calculator that adds up today's caffeine and shows what's left in your body, now and at bedtime.
0.0(0 ratings)
by Navid Moazzez·Updated Oct 3, 2026·3 min read·Navid.me is reader-supported. When you buy through links on this site, I may earn an affiliate commission. Learn more.You
Entered once, used by every health calculator here, and saved only in this browser.
Your result
You
Entered once, used by every health calculator here, and saved only in this browser.
Your result
Keep it
Save this report as its own page: pick a style, then download the HTML file or print it to PDF.
These calculators give general estimates for healthy adults, not medical advice. Talk to your doctor before you change how you eat or train, especially if you're pregnant, take medication or have a health condition.
Embed this tool on your site
Paste the code into any page: WordPress, Webflow, Squarespace, Ghost or plain HTML. It's free with the credit under it, which links back to navid.me.
This free caffeine calculator adds up the caffeine in your drinks today and estimates how much is still in your body, now and at bedtime.
Add each coffee, tea, soda or energy drink and when you had it, and it shows your total against the FDA's daily amount, with the curve for the next 24 hours.
I built it because the afternoon coffee is still in you at night, and a curve makes that easy to see.
TL;DRKey takeaways
What is a caffeine calculator?
A caffeine calculator adds up the caffeine from your drinks and estimates how much is left in your body over time.
This one checks your day against the FDA's 400 mg, or ACOG's 200 mg if you're pregnant, and draws the next 24 hours.
How it works
The calculator works it out on your device, and your numbers stay there.
How much caffeine is too much?
The FDA cites 400 mg a day for most adults as an amount not generally linked to negative effects. It also says sensitivity and how fast people clear caffeine vary widely.
It estimates toxic effects like seizures can come with about 1,200 mg taken quickly, which is why pure caffeine powders are dangerous.
Caffeine in pregnancy
ACOG Committee Opinion 462 says moderate caffeine, under 200 mg a day, doesn't appear to be a major factor in miscarriage or preterm birth. The calculator uses 200 mg as the limit when you pick pregnant.
How long caffeine lasts
A 2009 study of 59 healthy men found an average half-life of 4.3 hours in non-smokers and 3.0 in smokers. Half of it is gone in that time, half of the rest in the next, and so on.
Individual half-lives vary, so treat the curve as the shape to expect.
A worked example
Here's the example the calculator loads: a coffee 6 hours ago, another 2 hours ago and an energy drink now, with bed in 8 hours.
That's 504 mg today, 104 mg over 400. About 343 mg is in your body now, and about 94 mg will still be there at bedtime.
Mistakes to avoid
These are the slips that come up most.
- Counting a large coffee-shop cup as 1 standard cup
- Forgetting caffeine in supplements, gum and some over-the-counter medicines
- Assuming decaf has none, when it has 2 to 15 mg a cup
- Judging tonight's sleep by how awake you feel now
Who is the caffeine calculator for?
It's for coffee and energy-drink drinkers who want to sleep well, and these tools help around it.
- Sleep calculator – for a bedtime that ends a sleep cycle
- Water intake calculator – for a day's water
- Morning routine generator – for a morning that starts without the rush
Move your last coffee earlier, and watch the bedtime number drop.
Plan your money with your AI
Take your numbers further in
Caffeine Calculator FAQs
Questions about the caffeine calculator? Here's what to know.
It adds up the caffeine in your drinks and estimates how much is left in your body over time.
For most adults, the FDA cites 400 mg a day as an amount not generally linked to negative effects.
A 12-ounce brewed coffee typically has 113 to 247 mg, according to the FDA.
Half of it is gone in about 4.3 hours on average for non-smokers, and 3.0 for smokers, in a 2009 study.
The rest keeps halving at the same pace.
ACOG says under 200 mg a day doesn't appear to be a major factor in miscarriage or preterm birth.
Yes, decaf coffee typically has 2 to 15 mg in an 8-ounce cup, the FDA says.
41 to 246 mg in 12 ounces, the FDA says, so check the label.
Smokers cleared caffeine faster in the 2009 study, with a half-life of about 3.0 hours.
Yes, it's free with no sign-up.
It runs in your browser, and your numbers stay on your device.
I did.
I'm Navid Moazzez, and I made the caffeine calculator as one of my free tools on navid.me.
More about me.
Navid Moazzez
AI business strategist & AI OS builder
Navid Moazzez helps creators and founders master AI and build their own AI Operating System (AI OS) to automate their business and life.
Navid.me is reader-supported. When you buy through links on this site, I may earn an affiliate commission. Read the affiliate disclaimer.
Related calculators
More free tools
Related MCP servers & CLIs
Bluesky
Substack
Threads
Mastodon
TikTok
Apple Podcasts
Free AI newsletterThe most actionable AI newsletter for founders
Every week, get proven AI strategies, curated tools, and step-by-step systems to grow your audience, create better content, and build a profitable creator business.
No fluff, no filler, no BS. Just five minutes each week that might level up your online business and life.
P.S. Sign up now to get free access to my ultimate AI tools guide for creators.
