Ainonymity Calorie Counter · The method

Why calorie apps give you different numbers.

Published 26 September 2026

Put the same age, height, weight and week into five calorie counters and you can get five daily targets, hundreds of calories apart. The difference is rarely a bug. Every step from your details to a number has more than one published answer, and each calculator picks one. These are the forks, and the branch this app takes at each.

1. The equation for your resting energy

Every target starts from an estimate of what your body burns at rest, and there are several equations for it. This app uses Mifflin-St Jeor. Australia and New Zealand’s reference values use Schofield; European reference work uses Henry. Given the same person, they return different resting figures — before activity or a goal is even considered.

A 2005 systematic review found Mifflin-St Jeor the most accurate of the common equations, landing within 10% of measured resting metabolism in most adults. On a 2,500 kcal target, that is a band of about ±250 kcal, which is why every figure here is a starting point. The whole method is on its own page.

2. The activity multiplier — the biggest lever

Resting energy is multiplied by an activity factor to reach your maintenance figure, and this is where calculators part company most. Moving the factor from a desk job (1.4) to strenuous physical work (2.0) changes the same person’s maintenance by roughly 40% — more than any choice of equation. And it rests on a self-description, which is the least reliable input of all.

You may have met a five-step ladder that starts at 1.2 for “sedentary”. The bodies this app cites — EFSA and FAO / WHO / UNU — publish lifestyle values that start at 1.4. On a resting figure of 1,600 kcal, that gap alone is 1,920 against 2,240 kcal a day.

This app asks two questions instead of one, as EFSA itself does: how physical your work is, and how much exercise you do a week, each answered from EFSA’s own published values.

3. The goal adjustment

For weight loss, the published answers differ by country. A 2013 United States guideline prescribed a deficit of 500 or 750 kcal a day; a 1998 US evidence report gives 500 to 1,000. The United Kingdom’s current guideline, NICE NG246, removed its earlier 600 kcal figure in 2025 and now names no daily amount. Canada’s 2020 guideline recommends individual nutrition therapy with a dietitian rather than a single figure.

For weight gain, no national body publishes a recommended surplus for healthy adults.

This app takes 500 kcal off for weight loss, the lower of the US pair (less when that would cross its floor — see below), and adds 300 for weight gain — a conservative figure that is our own choice, and says so on screen.

4. The floor, and what happens below it

A calculator can print whatever number the arithmetic produces, or quietly clamp it to a minimum. This app suggests nothing below 1,200 kcal a day, or 1,500 for men. When the usual 500 kcal deficit would cross that floor, it offers the floor with a smaller deficit and says so on screen — down to a deficit of 300 kcal a day, the smallest the NHLBI’s evidence report names. Below that, and for any goal that is unsafe for your details, it offers no target at all and says why. Those two floors are our own choice, and the page on how targets are calculated explains where they came from.

5. Rounding and units

A target is rounded before you see it, and the direction matters. This app rounds to a multiple of 50 in the unit you read — calories or kilojoules — and always towards your goal, so rounding never quietly weakens it.

6. The macro split

Even with the same energy target, the recommended split differs. Protein, for example, is 10–35% of energy in the United States and Canada, 15–25% in Australia and New Zealand, and 10–20% in the Nordic countries — and EFSA publishes no range for it. This app lets you choose whose ranges colour your figures, and shows all five side by side on macro ranges by country.

7. The food data underneath

A target is only half the comparison; the other half is what you log against it. The same meal can carry different figures depending on where the entry came from — a laboratory-analysed government table, a product label, or an entry typed in by another user. This app’s ingredient search uses six national government tables, and its barcode scanner uses the USDA’s branded foods data; every source is listed. Its photo estimates are the one part that has not been measured against weighed meals, and its Terms of Use say so.

What to do with this

Pick one calculator and stay with it, so the numbers are at least consistent with each other. Treat the target as a starting point, watch what happens over a few weeks, and adjust from there — that is what a ±10% estimate is for. And prefer an app that shows its working, so that when two numbers disagree, you can see which fork they took.

Where all of this comes from

• Mifflin MD et al., 1990 — the resting-energy equation this app uses.
• Frankenfield D et al., 2005 — the systematic review comparing predictive equations.
• NHMRC / New Zealand Ministry of Health, 2006 — Australia and New Zealand’s energy reference values, built on Schofield.
• FAO / WHO / UNU, 2001 — maintenance as resting energy times an activity level.
• EFSA, 2013 — the activity values for work and for exercise.
• Black AE et al., 1996 — the lifestyle bands EFSA reproduces, from 574 doubly-labelled-water measurements.
• AHA / ACC / TOS, 2013 — the 500 or 750 kcal deficit. Retired in 2026.
• NHLBI, 1998 — the evidence report behind a 500–1,000 kcal deficit.
• NICE NG246, 2025 — the UK guideline that sets no daily figure.
• Wharton S et al., Obesity in adults: a clinical practice guideline, CMAJ 2020 — Canada’s individualised approach.
• Helms ER et al., 2023 — small against large energy surpluses; the background to a conservative +300.

See every fork on screen — have a look at Ainonymity Calorie Counter, or compare calorie apps side by side.