What CaffCalc is
CaffCalc is a free caffeine safety calculator and a small library of research-compiled articles about how caffeine behaves in the body. It exists to answer a question that most search results answer badly: how much caffeine is too much — for me, specifically?
The site is independent and free to use. It has no sponsor, no affiliation with any beverage manufacturer, and at present carries no advertising.
Why it was built
Almost every article about caffeine repeats the same number: 400 mg a day. That figure comes from the FDA and it is a reasonable population-level benchmark for healthy adults — but it is a single number applied to everyone.
A 50 kg adult and a 95 kg adult do not have the same tolerance. A pregnant reader has a materially different limit. A 15-year-old has a different one again. And people vary enormously in how quickly they clear caffeine. Repeating 400 mg to all of them is not helpful, and in some cases it is misleading.
CaffCalc was built to do the arithmetic that those articles skip.
What makes it different
Rather than returning a flat figure, the calculator works from your own inputs:
Body weight
Limits are calculated on a milligrams-per-kilogram basis, in line with how the EFSA expresses its assessment, rather than as one fixed total.
Age band
Separate ceilings for children, teenagers, adults and older adults, with progressively more conservative figures outside the adult band.
Pregnancy & breastfeeding
A reduced limit reflecting the under-200 mg per day figure described by ACOG.
Personal sensitivity
A self-reported sensitivity setting, for readers who already know that caffeine hits them harder or lighter than average.
It also runs entirely in your browser. Your weight, age and pregnancy status are never sent to us — see the Privacy Policy.
Who runs the site
CaffCalc is an independently owned and operated project, not a company, a clinic or a medical organisation.
If you need advice about your own health, that conversation belongs with a qualified professional. See our Terms of Use.
Editorial approach
Articles on CaffCalc are compiled from published guidelines and peer-reviewed research, and are checked against their sources before publishing. The references we work from are:
- U.S. Food & Drug Administration — consumer caffeine guidance
- European Food Safety Authority — scientific opinion on the safety of caffeine
- USDA FoodData Central — caffeine content of foods and beverages
- American College of Obstetricians and Gynecologists — caffeine in pregnancy
- PubMed — peer-reviewed literature on caffeine metabolism and effects
- Manufacturer nutrition labels, for the caffeine content of specific branded products
Our working rules:
- Every numeric claim is traceable to a source we link to.
- Where the evidence is mixed or weak, we say so rather than picking the more dramatic side.
- Where a caffeine figure is a range, we report the range instead of averaging it into false precision.
- We do not claim medical review that has not happened.
Found an error? We would genuinely like to know. Email salmorejo2024@outlook.com with the page and the figure you are questioning — a link to a better source is especially welcome — and we will correct it or explain our reasoning.
Get in touch
Corrections, questions and suggestions for what to cover next: salmorejo2024@outlook.com. You can also start with the calculator, the science page, or the blog.