Methodology
How this calculator actually works
Eight science-backed formulas give you a starting number. The tracker then measures your real burn from your weigh-ins and daily calorie totals, tells you how much of the estimate is your own data, and keeps every target inside visible safety limits. No black box.
By FitnessVolt. Updated .
1. The 8 formulas we support
BMR (basal metabolic rate) is the base floor: the calories your body burns at rest. TDEE is your total daily expenditure. For adults 19 and over, your TDEE comes from the 2023 DRI EER equations and the BMR shown beside it is Mifflin-St Jeor. Under 19, the calculator uses Mifflin-St Jeor. Enter your body fat percentage and the calculator switches to Katch-McArdle, which works from your lean mass: your BMR comes from it, and your TDEE is built on that BMR. Enter body fat and pick a sport under Sport / Discipline, and it uses Cunningham instead. You can compare all eight formulas side-by-side in your result.
| Formula | Best for | Needs | Year |
|---|---|---|---|
| 2023 DRI EER | Default TDEE for adults 19+. Fitted to doubly labeled water measurements of total daily expenditure. | Age, sex, weight, height, activity | 2023 |
| Mifflin-St Jeor | The BMR shown in your result. Best-tested static formula for the general population. | Age, sex, weight, height | 1990 |
| Harris-Benedict (original) | Historical reference. Tends to overestimate for modern adults. | Age, sex, weight, height | 1919 |
| Harris-Benedict (revised) | Classic clinical reference. Slightly overestimates for modern sedentary adults. | Age, sex, weight, height | 1984 |
| Katch-McArdle | Lean or muscular people who know their body fat. Used when you enter body fat and leave Sport / Discipline on General Fitness. | Weight, body fat % | 1996 |
| Cunningham | Lean, highly trained people. From a 1980 reanalysis of healthy adults; higher intercept than Katch-McArdle. Used when you enter body fat and pick a sport. | Weight, body fat % | 1980 |
| Schofield | WHO-endorsed baseline used in international nutrition standards. | Age, sex, weight | 1985 |
| Owen | Weight-only resting equations. A quick cross-check on the others. | Sex, weight | 1986-87 |
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 doubly-labeled-water (DLW) measurements, 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. The 2023 equations rest on a much larger DLW dataset than the 2005 EER equations they replace.
We default to DRI EER for adults 19 and older. Under 19, the calculator uses Mifflin-St Jeor instead.
National Academies of Sciences, Engineering, and Medicine (2023). Dietary Reference Intakes for Energy.
3. How much of your estimate is your own data
Your dashboard shows your estimated burn with a range and a label. The label tells you how much of the estimate comes from your own weigh-ins and calorie totals, and how much still comes from the formula. A measured week is one with enough weigh-ins and calorie totals for the tracker to work out your burn; section 4 has the numbers. The range is where your true burn should sit about 8 times in 10. It never gets narrower than 100 calories either side.
Starting estimate
Before your first measured week
The estimate is the calculator's formula number and none of it is your data yet. The range is wide: about a quarter of the estimate either side, or roughly 640 calories at 2,500.
Calibrating: N% your data
From your first measured week
Each week that has enough weigh-ins and calorie totals to measure your burn usually raises N and narrows the range. N has no fixed steps. Steady daily weigh-ins and full logging raise it faster than a few scattered entries.
Measured
From 95% your data
The label reads "Measured from your weigh-ins and calories". It never reaches 100%, because your burn changes as your body and training change, and the tracker keeps checking it every week.
Only measured weeks add your data. A week you save with calorie totals that still falls short of the measuring rule adds nothing, and N can dip a point or two that week, because the tracker allows for your burn drifting while it could not measure it. A week with weigh-ins alone, or fewer than 4 calorie days, leaves N where it is.
4. The weekly update
You log your weight and your daily calorie total from any app. Once a week, with your first weigh-in after the week is ready, the tracker looks back over your recent days. A week is ready when it has 3 or more weigh-ins and at least 7 days have passed since the last saved week. A ready week and a measured burn are different bars: 3 weigh-ins make the week ready, 8 across the last 28 days measure your burn.
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Your weight trend over 28 days
The tracker fits a straight line through up to 28 days of weigh-ins, so one salty dinner or a water spike barely moves it. It needs at least 8 weigh-ins over at least 14 days, counted from your first logged calorie day in that stretch.
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Your average daily intake
It averages your calorie totals over the same days. You need complete totals on at least 4 days, and on at least half the days in the stretch. If you mark a day as partial, the tracker leaves it out, so a day you stopped logging halfway does not drag the average down. Days you do not mark count as complete.
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Your measured burn
Intake minus the energy in your weight change gives the burn that fits your trend, counting 7,700 calories per kilogram. Eat 2,300 a day while losing 0.25 kg a week and your burn works out at about 2,575 a day. If more than 14 days pass between saved weeks, the first week back is saved without measuring your burn. Measuring starts again once you have 14 days of weigh-ins and calorie totals.
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Estimate first, then target
The tracker blends the measured burn into your estimate. Early weeks move it more and later weeks less, and it never moves more than 200 calories in one week, so a single odd week cannot swing your plan. Your target is then worked out again from the new estimate: your goal's deficit or surplus is applied, then the safety limits below. When the target moves by 25 calories or more, the dashboard shows the old and new numbers in one sentence. The new target applies straight away unless you have fixed your own target (see Safety). Tap Go back on the card to return to your old target, never below the floor.
Weigh-ins only, or fewer than 4 calorie days in the week? The tracker cannot measure your burn, so it never claims one. It runs a pace check instead: your 14-day weight trend against the rate your goal asks for, from 5 or more weigh-ins over at least 10 days. If you are off plan by 150 calories a day or more in two checks in a row, it suggests eating 100 calories more or less. Nothing changes until you accept the suggested target on the card, and pace changes stop at 200 calories in total. While you have fixed your own target, pace checks pause. Your first measured week replaces the pace change with a measured estimate.
Already log in MyFitnessPal or Cronometer? Import the export file and the tracker replays your last 26 weeks of weigh-ins and calories in one go, so your estimate is ready when the import finishes. Days older than 26 weeks stay in your log without a check-in.
5. Safety promise
Every calorie target runs through the same guardrails in code before it appears on your screen.
Minimum calorie floor
The calculator never sets a daily target below the higher of your BMR x 1.2 or 1,200 kcal for women and 1,500 kcal for men, and a fat-loss deficit never goes past 25% of your TDEE or a loss of 1% of your body weight per week. If your goal rate would break either limit, the target stops at the limit and the result tells you why. For a very small or very sedentary person that minimum can sit above their TDEE; a fat-loss target then stays at TDEE, with no deficit, and the result says to talk to a doctor first.
Setting your own target
You can fix your daily target yourself in Settings. It stays until you clear it. A measured update still tells you what your plan now says, with a button to switch back to it. The tracker refuses a fixed target below the floor. If your burn itself is under the floor, the lowest target you can fix is your burn. A target you had set by hand before this version of the tracker stays fixed the same way.
Diet breaks on long cuts
Plan a 1-2 week diet break at maintenance every 8-12 weeks of dieting, as our weight loss guide explains. The tracker does not schedule the break for you, so put it in your plan when you start a long cut.
RED-S risk detection
Relative Energy Deficiency in Sport has 3 severity tiers. We estimate your energy availability from logged intake, logged training time and fat-free mass, and raise a visible warning with a medical disclaimer when it stays below 30 kcal per kg of fat-free mass on 3 or more days in a week.
Anti-diet-culture stance
No scale-shame copy, no "cheat day" language, no stigmatization of body size.
6. What this calculator does NOT do
These are the limits.
- 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 and deficit-duration flags are risk indicators, not diagnoses.
- It does not work out energy needs for pregnancy or breastfeeding. Those change from one stage to the next, so set them with your doctor, midwife or a registered dietitian.
- It does not perform OCR on food photos or scan meals visually. You enter each day's calorie total, scan a barcode, or import your history from MyFitnessPal or Cronometer.
- 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?
For adults 19 and over, the calculator estimates TDEE with the 2023 DRI EER equations. The BMR it shows is Mifflin-St Jeor. Enter your body fat and it switches to Katch-McArdle; enter body fat and pick a sport under Sport / Discipline, and it uses Cunningham. Both work from lean mass. The bigger accuracy gain comes from calibrating with your logged weight and calories, not from picking a different formula.
What does "Calibrating: N% your data" mean?
It is the share of your estimate that comes from your own weigh-ins and calorie totals. The rest still comes from the calculator formula. Before your first measured week the estimate is the formula number. Each week with enough data to measure your burn usually raises the share: at least 8 weigh-ins over 14 days or more, with complete calorie totals on at least 4 days and on half the days. At 95% the label changes to "Measured from your weigh-ins and calories". The range beside the estimate is where your true burn should sit about 8 times in 10.
Why did my calorie target change?
Your weekly update measured a burn that differs from your estimate, so the estimate moved. Your target was then worked out again from the new estimate: your goal's deficit or surplus is applied, then the safety limits. The estimate never moves more than 200 calories in one week. The dashboard shows the old and new target in one sentence, and Go back on that card returns you to the old one, never below the floor. If you only weigh in, a pace suggestion changes nothing until you accept it.
Is a calorie deficit safe?
Only within limits. The calculator never sets a daily target below the higher of your BMR x 1.2 or 1,200 kcal for women and 1,500 kcal for men, and a fat-loss deficit never goes past 25% of your TDEE or a loss of 1% of your body weight per week. If your goal rate would break either limit, the target stops at the limit and the result tells you why. For a very small or very sedentary person that minimum can sit above their TDEE; a fat-loss target then stays at TDEE, with no deficit, and the result says to talk to a doctor first. It also estimates energy availability from your logged intake, logged training time and fat-free mass, and shows a warning when it looks too low.
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, so the calculator corrects them with your observed weight change. If you need medical nutrition therapy, please work with a qualified professional.
Ready to run the numbers?
Thirty seconds to your first estimate. About fourteen days of weigh-ins and calorie totals until your own data starts steering it.
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.