Show your work.
Every formula in this engine is published, cited, and verifiable. No hidden multipliers. No "trust me, I'm a coach." Pull our citations, plug your numbers, and re-derive every output yourself.
Three commitments
that compound trust.
Every output, cited.
Every number this engine returns lists its source — Mifflin–St Jeor (J Am Diet Assoc, 1990), ISSN Position Stand on Protein (2017), Schoenfeld 2016 hypertrophy volume meta. No black boxes.
No silent math upgrades.
If we change a formula coefficient, you'll see a changelog entry. Past calculations remain reproducible. Your Blueprint from v1.0 will still be derivable when v2.0 ships.
Bring your own second opinion.
Open source core arriving Q3 2026 with a public bug bounty for math errors. Until then, every formula is documented below — pull a calculator, run our inputs, get the same outputs. If you can't, file an issue and we ship a fix in the next deploy.
Every formula
in the engine.
12 calculators, 7 peer-reviewed sources. Click any to see the citation + plug-in form.
| Tool | Formula | Source · Year | Audit |
|---|---|---|---|
| BMR · Mifflin | 10·W + 6.25·H − 5·A + s | J Am Diet Assoc · 1990 | Run → |
| BMR · Katch-McArdle | 370 + 21.6·LBM | Katch & McArdle · 2002 | Run → |
| TDEE | BMR × activity factor (1.2–1.95) | ACSM Position Stand · 2018 | Run → |
| Protein target | 1.6–2.2 g/kg body weight | ISSN · 2017 | Run → |
| Body fat % · Navy | 495 / (1.0324 − 0.19077·log10(W−N) + 0.15456·log10(H)) − 450 | U.S. Navy Method · 1981 | Run → |
| BMI · Asian-Pacific | W / H² (cutoffs: 23/27.5) | WHO Expert Consultation · 2004 | Run → |
| 1RM · Epley | W × (1 + R/30) | Epley · 1985 | Run → |
| 1RM · Brzycki | W × (36 / (37 − R)) | Brzycki · 1993 | Run → |
| Hypertrophy volume | 10–20 sets/muscle/week | Schoenfeld et al. · 2016 | Library → |
| HIIT zones | %HRmax = 220 − age | ACSM HIIT Stand · 2022 | Today → |
| Cycle-sync (women) | Phase-adjusted RPE | Sims et al. · 2023 | Read → |
| Indian micronutrients | ICMR-NIN RDA tables · 2020 | ICMR · 2020 | Diet hub → |
Audit your own BMR.
Sample worked example. Plug your numbers, get the same answer. If you don't, mail us — we ship a fix.
BMR for a 32-year-old male, 75 kg, 178 cm
BMR = 10·W + 6.25·H − 5·A + 5
BMR = 10·75 + 6.25·178 − 5·32 + 5
BMR = 750 + 1112.5 − 160 + 5
BMR = 1707.5 kcal/day
Open /bmr.html in another tab. Plug 75 / 178 / 32 / male. Engine returns 1,708 kcal/day (rounded). If yours doesn't match, screenshot & mail.
What comes next.
/api/validate · signed JSON for any outputChangelog auto-publishes to /changelog. No silent updates.
Your body deserves
verifiable math.
Most fitness apps quote a TDEE without showing the formula. So a 75 kg man might see 2,100 from one app and 2,400 from another — both "scientific". Cumulative error over a 12-week cut: 25,000 kcal · 3.5 kg of mis-attributed fat loss / gain.
When the math is open, you can pin down where the difference comes from (activity factor assumed? Mifflin or Harris-Benedict?) and pick what fits your body, not a black box's average.
Honest math also means honest expectations. If you know your BMR is 1,650 and the engine says you can lose 0.5 kg/week at a 500 kcal deficit, you can verify the assumption (1 kg fat ≈ 7,700 kcal) and stop chasing magic.
FitnessByMaddy's whole stance is that information transparency creates better outcomes than fancy metaphors. This page is the proof.
Ready to audit your body?
Start with the Blueprint — it derives all 12 outputs from one form. Every output cites its formula.
Open the Blueprint →