Transparent calculator · Caffeine 1.0
Caffeine Dose & Timing Calculator
Total caffeine from several sources, calculate mg/kg and place the last dose in bedtime context.
Purpose
What this tool is for
Use this to audit one day of labelled caffeine intake and see neutral public-health and sleep-timing cautions.
Audience
Who it is for
Adults aged 18+ entering known caffeine amounts from labels or published café nutrition data.
Input glossary
What each field means
| Input | Unit or choice | Why it matters |
|---|---|---|
| Body weight | kg or lb | Converts the daily total and each dose to mg/kg. |
| Context | healthy adult / pregnant or breastfeeding | Selects the relevant EFSA daily reference comparison; it is not a safety verdict. |
| Bedtime | time | Used only to show elapsed time after the final logged dose. |
| Doses | mg + time | All entries refer to the 24 hours before the next bedtime. Include food, drinks, supplements and medicines. |
Method · Caffeine 1.0
The formula or decision logic
Daily total = sum of entered doses. Relative dose = total mg ÷ body weight in kg.
The final dose is the entry closest to the next bedtime. A 100 mg dose within six hours produces a conservative sleep-timing caution; six hours is a display rule, not a universal cutoff.
For healthy adults, comparisons use 200 mg per single dose and 400 mg/day public-health references. Pregnancy/breastfeeding comparison uses 200 mg/day. None is presented as a guarantee.
References support the method or context; they do not validate an individual result. See the sources.
Worked example
Example, not a recommendation: two labelled doses
- Taylor weighs 70 kg and logs 150 mg at 08:00 plus 100 mg at 16:00 before a 23:00 bedtime.
- Total: 150 + 100 = 250 mg. Relative total: 250 ÷ 70 = 3.57 mg/kg.
- The final dose is 100 mg, seven hours before bedtime.
Interactive calculator
Audit one day of caffeine
Nothing you enter is sent to our server. Calculation happens in this browser.
Limitations
What the result cannot tell you
- Product and café values can vary widely.
- Body weight does not capture genetic, medication, pregnancy or tolerance differences.
- The tool does not calculate caffeine remaining in the body or predict sleep.
- Pure or highly concentrated caffeine can be dangerous and is outside the tool’s intended use.
Questions specific to this tool
Frequently asked questions
Is 400 mg a safe limit for everyone?
No. It is a population reference for most healthy adults, not a personal safety guarantee. Some people experience effects at lower amounts.
Why can caffeine affect sleep when I feel tired?
Feeling tired does not mean caffeine has stopped acting. Timing and sensitivity vary, so the tool shows context rather than a predicted clearance time.
Does body weight determine sensitivity?
It provides a useful relative-dose calculation, but genes, medications, pregnancy, regular use and health conditions also matter.
Can caffeine replace lost sleep?
No. It may temporarily change alertness but does not replace sleep or guarantee safe performance.
What if I take medication or am pregnant?
Use the pregnancy comparison only as context and discuss individual intake with an appropriate clinician or pharmacist.
Primary and official references
Sources
Caffeine topic and safety assessment
European Food Safety Authority · Current
Supports: Single-dose, daily and pregnancy reference valuesSpilling the Beans: How Much Caffeine is Too Much?
US Food and Drug Administration · Current
Supports: 400 mg context and variabilityFound a numerical or source issue? Send a correction with the page URL.