Method & Data
Every calculator's formula and every table's data source, in one place. If a page shows a number, this page tells you where it came from — and where it can't be trusted.
Formula inventory
| Tool / chart | Computation | Source |
|---|---|---|
| Caffeine taper calculator | weekly targets at −25% (or gentle 12.5%) until the chosen floor; ordering via greedy same-kind substitution (coffee → half-caff → decaf) from the 80-drink library | Taper pace and withdrawal timeline from Juliano & Griffiths' caffeine-dependence review; StatPearls |
| Calcium intake checker | 1,000 mg adults; 1,200 mg women 51+ (or postmenopausal) and men 71+; ceiling 2,000–2,500 mg | National Academies RDAs; Endocrine Society / NAMS postmenopause guidance |
| VO2 max calculator | Rockport 132.853 − 0.0769·lb − 0.3877·age + 6.315·male − 3.2649·min − 0.1565·HR; Cooper (distance_m − 504.9)/44.73; resting-pulse 15.3 × HRmax/HRrest | Kline 1987 (Rockport); Cooper 1968; Uth-Sørensen 2004; age-decade fitness norms |
| Perimenopause cycle tracker | cycle lengths from logged dates; STRAW+10 rules: recurring ≥7-day differences between consecutive cycles, ≥60-day gaps, 12-month amenorrhea | STRAW+10 framework applied to user-logged data |
| Caffeine cutoff / timeline / when-to-stop | cutoff = bedtime − T½ × log₂(dose ÷ limit); one-compartment decay, 45-min absorption ramp | Base T½ 5 h; smoking ×0.6, estrogen contraceptives ×1.8, self-reported slow ×1.3 (lit. range 1.5–9.5 h) |
| Caffeine while breastfeeding | Milk peak 1–2 h after dose; ~1% of maternal dose transfers; 200–300 mg/day ceiling | NIH LactMed; Australian Breastfeeding Association |
| Alcohol while breastfeeding | Clearance 2–2.5 h per 12 g drink, linear in body weight (54 kg → 2.5 h … 82 kg → 2 h) | NIH LactMed clearance nomogram |
| Sleep cycles | Bed/wake times stepped in 90-min cycles minus sleep latency | Cycle length 80–110 min in the literature; 90 used as the honest middle |
| Protein targets (GLP-1 / perimenopause) | g/kg bands: 1.2–1.6 (GLP-1 joint advisory 2025; Delphi 2025: 1.2–1.5), 1.6–2.2 active midlife (Sims) | 2025 GLP-1 joint advisory & Delphi consensus; ISSN position stand; menopause-fitness literature |
| Water target (GLP-1) | 35 ml/kg + activity 350–750 ml + heat 500 ml | Commonly cited adult band vs EFSA adequate intake 2.0/2.5 L |
| Fiber target | 25/38 g (F/IOM) or 28/34 by age | Institute of Medicine adequate intakes; FDA DV 28 g |
| Iron target | 18 mg women 19–50 with periods, 8 mg after; ×1.8 plant-based | National Academies (IOM) RDAs |
| Menopause symptom score | 11 items × 0–4, three domains, 0–44 | Menopause Rating Scale (Heinemann et al. 2003/2004) |
| Perimenopause staging | 7-day / 60-day / 12-month cycle rules | STRAW+10 framework |
| Heart rate zones | Fox 220−age; Tanaka 208−0.7×age; Gulati 206−0.88×age (women); zones 50–100% max; Karvonen optional | Fox 1971; Tanaka 2001; Gulati 2010 |
| Sit-to-stand | 30-second chair stands vs age/sex norms | CDC STEADI |
| Food data (all charts and food pages) | per 100 g from USDA; per 100 kcal = ÷kcal×100; DV = FDA adult values (21 CFR 101.9; potassium 4,700 mg) | USDA FoodData Central (SR Legacy / Foundation), synced per entry with fdc_id |
Data pipeline
Food values come from USDA FoodData Central: each of the
360 foods carries its own fdc_id pinned to a specific entry, and a sync
script re-fetches official values while preserving hand-written names and notes. The last sync
date shows on each food page. Where USDA doesn't report a nutrient, the page shows a dash —
never an estimate. Drink caffeine values are per labeled serving, each with its own cited source (brand, USDA or CSPI; a few marked unverified), from FDA/USDA references and
manufacturer labels.
What the math can't do
Half-life formulas describe populations, not you; screening scales suggest conversations, not diagnoses; RDAs are population floors, not personal prescriptions. Every tool on this site is a better-informed question for your clinician, not a replacement for one. Health decisions belong to you and your care team; the numbers here just make the conversation concrete.