Generic fatigue advice is everywhere. These tools give you specific, personal numbers — how much caffeine is actually in your system right now, whether your blood results are in the optimal range for energy, what your medication is doing to your sleep.
No account needed. Results are instant and calculated in your browser.
If You drink coffee daily → Caffeine Calculator
Find out how much caffeine is still active in your system and whether your cut-off time is too late.
If You drink alcohol → Alcohol & Sleep Calculator
Alcohol is one of the most common causes of unrefreshing sleep — even in small amounts. See the exact impact tonight.
If You've had blood tests recently → Lab Result Interpreter
Standard 'normal' ranges are broad. Find out whether your iron, B12, vitamin D, or thyroid levels are in the optimal range for energy.
If You take regular medication → Medication Fatigue Checker
Over 200 common medications list fatigue as a side effect — many are prescribed for conditions unrelated to tiredness.
If Fatigue is affecting your work → Fatigue Cost Calculator
Quantify the productivity loss in hours and salary — useful for understanding the cost of not addressing fatigue.
Yes — all tools are completely free. No account, no email required. Results are calculated instantly in your browser.
The calculators use the same pharmacokinetic models used in clinical research (e.g., caffeine's 5.5-hour half-life, alcohol clearance at ~1 unit/hour). Individual variation exists — genetics, body weight, and liver function all affect results — but the outputs are a reliable starting point for most adults.
The tools give you specific, quantitative answers about one factor (caffeine timing, alcohol impact, blood results). The fatigue quiz analyses 15+ factors together and identifies which combination is most likely driving your tiredness.
Yes. Lab reference ranges are set to catch pathology, not to identify the optimal level for energy. Ferritin 'normal' starts at 12 μg/L, but many people don't feel well below 50. The interpreter flags these functional gaps.
The 2-minute fatigue quiz analyses 15+ factors together — sleep, nutrition, stress, caffeine, blood markers — and identifies which combination is most likely driving your tiredness.
Take the free analysis →2 minutes · no account needed · instant results