Methodology
How this calculator actually works
Eight science-backed formulas, a confidence model you can trust, a 14-day calibration loop, and visible safety guardrails. No black box.
1. The 8 formulas we support
BMR (basal metabolic rate) is the base floor - calories your body burns at rest. TDEE multiplies BMR by an activity factor to estimate total daily expenditure. The calculator picks a default formula from your inputs and lets you compare all eight side-by-side.
| Formula | Best for | Needs | Year |
|---|---|---|---|
| 2023 DRI EER | Default for adults 19+. Built from 8,600 DLW measurements. | Age, sex, weight, height, activity | 2023 |
| Mifflin-St Jeor | Commonly recommended static formula for the general population. | Age, sex, weight, height | 1990 |
| Harris-Benedict (revised) | Classic reference. Slightly overestimates for modern sedentary adults. | Age, sex, weight, height | 1984 |
| Katch-McArdle | Strength athletes and lean physiques. More accurate when body fat is known. | Weight, body fat % | 1996 |
| Cunningham | Elite athletes. Higher lean-mass coefficient than Katch-McArdle. | Weight, body fat % | 1980 |
| Oxford (Henry) | Adult BMR estimates tailored to tropical and mixed populations. | Age, sex, weight, height | 2005 |
| Schofield | WHO-endorsed baseline used in international nutrition standards. | Age, sex, weight | 1985 |
| Army / Military | Tuned for active-duty personnel. Higher activity multipliers. | Age, sex, weight, height | various |
No single formula is "most accurate" for every person - each one has a population it fits best and a population it misses. The real accuracy gain comes from calibration, not from picking a different starting formula.
2. Why the 2023 DRI EER is the new default
The 2023 Dietary Reference Intakes (DRI) refresh updated the Estimated Energy Requirement (EER) equations using 8,600 doubly-labeled-water (DLW) observations - the gold standard for measuring energy expenditure in free-living humans.
DLW tracks two isotopes (deuterium and oxygen-18) as they leave the body, letting researchers back-calculate total daily energy expenditure without guessing at activity. This replaces the older 2005 EER equations, which were based on roughly 1,200 measurements.
We default to DRI EER for adults 19 and older. For younger users, pregnancy, or lactation, different coefficients apply automatically.
Institute of Medicine / National Academies (2023). Dietary Reference Intakes for Energy. Chapter 5: Energy.
3. Confidence: Low / Medium / High
Every calorie target on your dashboard shows a confidence label. It is the single most important number to understand.
Low
Days 0 - 6
We have your inputs and a formula estimate, no observed data yet. Your target could be off by 300+ calories either way. Keep logging weight and calories - the number will tighten quickly.
Medium
Days 7 - 13
We have your first weekly check-in and can back-calculate an observed TDEE from your weight trend. The target is adjusted and usually within ±200 calories of your true maintenance.
High
Day 14+
Your logged intake and weight trend agree over two cycles. The target has a tighter confidence range, and the system keeps nudging it as your body and training load change.
Confidence is earned by logging. The same calibration cadence powers launch-mode access and the later paid model.
4. The 14-day calibration loop
The calculator does not stop after your first number. Every day you log weight and calories, two pieces of data enter a feedback loop:
-
Observed weight change over the week
We average your weigh-ins across the week (you need at least 4 entries for a valid signal - daily fluctuations mean a single reading is noise).
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Average daily calorie intake
If you logged most days, we trust the average. If you skipped days, we mark the week incomplete and wait.
-
Back-calculated observed TDEE
From those two signals we compute an observed TDEE estimate that fits the way your weight changed. That is distinct from the formula estimate.
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Target adjustment
If observed TDEE differs from the current target, we nudge the target - never more than a few hundred calories per adjustment - so next week aligns with your goal. The dashboard shows the change and the reason.
After two full cycles (14+ days), the system has enough evidence to show a calibrated TDEE estimate based on your logged trend, not only a population average.
5. Safety promise
Safety is not a marketing line - it is enforced in code. Every calorie target runs through the same guardrails before it appears on your screen.
Minimum calorie floor
Targets never drop below the higher of BMR × 1.2 or 1,200 kcal (women) / 1,500 kcal (men). If your goal rate would push you lower, we raise the target back to the floor and tell you why.
Deficit duration limit
After 12 continuous weeks in a deficit, we recommend a diet break to restore metabolic flexibility. The recommendation is visible, not hidden behind a paywall.
RED-S risk detection
Relative Energy Deficiency in Sport has 3 severity tiers. We flag patterns in your logs (chronic low intake, menstrual disruption, resting heart-rate drift) and raise a visible warning with medical disclaimers when the risk rises.
Restrict-binge alert
Large day-to-day calorie swings (very-low days followed by very-high days) are flagged early. We do not shame the pattern - we surface it and offer context.
Cycle-aware adjustments
For users who track menstrual cycles, plateau detection is suppressed during luteal-phase water retention, and TDEE is adjusted for phase-specific expenditure changes.
Anti-diet-culture stance
No scale-shame copy, no "cheat day" language, no stigmatization of body size. The AI advisor stays silent rather than deliver hollow motivation.
6. What this calculator does NOT do
Honesty about the edges is part of the product.
- It does not replace a registered dietitian or physician. For medical nutrition therapy, clinical eating-disorder care, or managed chronic conditions, please work with a licensed professional.
- It does not diagnose medical conditions. The RED-S, deficit-duration, and restrict-binge flags are risk indicators, not diagnoses.
- It does not perform OCR on food photos or scan meals visually. You log food by search, barcode, or saved meal.
- It does not time macronutrients by the hour. Daily totals are what the science supports.
- It does not guess harder when your inputs are off - it corrects through observed weight change. Logging beats input precision.
- It does not share, sell, or advertise on your logged data. See the privacy policy.
Frequently asked questions
Which TDEE formula should I use?
No single formula fits every person. The 2023 DRI EER equations were derived from 8,600 doubly-labeled-water measurements and are our default for adults 19+. Mifflin-St Jeor and Harris-Benedict remain useful for many inputs. Katch-McArdle and Cunningham are better suited when a body-fat percentage is known, because they compute BMR from lean mass. The accuracy gain comes from calibration with logged data, not from picking a different static formula.
What does "Low / Medium / High" confidence mean?
Low: we have only your inputs, no observed data yet. Your target is a formula estimate and could be off by 300+ calories in either direction. Medium: you have logged 7+ days of weight and calories, and we have back-calculated a first-pass observed estimate. High: you have logged 14+ days and the weight trend agrees with our calorie model, so we can show a higher-confidence adaptive target.
Why did my calorie target change?
After your first weekly check-in, the calculator compares your logged intake against your weight trend. If your body lost or gained weight faster or slower than a formula predicts, your observed TDEE differs from your estimated one. We nudge the target toward reality in small steps so your weekly rate of change matches your goal. Your dashboard shows a "why your calories changed" entry for every adjustment.
Is a calorie deficit safe?
Only within limits. This calculator enforces a minimum floor: targets never fall below the higher of BMR x 1.2 or 1,200 kcal (women) / 1,500 kcal (men). We also flag RED-S risk patterns (chronic low energy availability, menstrual irregularities, resting-heart-rate drift). If your inputs and logs suggest RED-S risk, we surface a visible warning and refuse to lower the target further without a coach or clinician override.
What does this calculator NOT do?
It does not replace a doctor or dietitian, and it does not diagnose medical conditions. It does not estimate macronutrient timing down to the hour. It does not perform OCR on food photos. Activity estimates from self-reported training are approximate - we correct them through observed weight change, not through better guessing. If you need medical nutrition therapy, please work with a qualified professional.
Ready to run the numbers?
Thirty seconds to your first estimate. Fourteen days to your calibrated TDEE.
Open the calculatorBuilt from measured metabolism research, not a generic multiplier alone.
These pages use published energy-expenditure research as the starting point, then the app improves the estimate with your logged weight and intake patterns when you calibrate.