As of 13 August 2026, AI can calculate your daily calorie needs.
This still needs a person who signs their name to it.
Can you do it?
5 minutesto a draft.
15 minutesto something you’d act on.
Cost, all in£0
Skill needednone
Who has to check ityou
What the alternative costsA purpose-built alternative is MacroFactor, which provides AI nutrition coaching that adjusts targets from logged data.
If this goes wrong: you follow an unsuitable calorie target, notice unwanted changes or poor wellbeing, and need to stop and reassess it rather than treating the estimate as a medical prescription.
What to actually do
Hand it to a person
The route this page recommends
A person who owns the outcome does this end to end, worth it when the failure is dear.
Do it yourself
Second choiceA chat interface, no skill needed, and roughly 15 minutes until you can act on the result.
How to actually do it
- Open a chatbot such as ChatGPT, Claude or Gemini and paste the prompt.
- Gather your age, height, current weight, sex used by the equation, usual activity level and whether you want to maintain, lose or gain weight.
- Replace each bracketed slot with your details, keeping the units clear, and send the prompt.
- Check that the chatbot has copied your age, height and weight correctly and has used the activity level you actually described.
- Recalculate the displayed equation with a calculator and compare your result with the chatbot's maintenance estimate.
- Treat the result as a starting estimate rather than a prescription, and speak to a GP or qualified health professional if you are under 18, pregnant, breastfeeding, have a relevant medical condition, take affected medication, have an eating-disorder history or have worrying symptoms.
- For urgent or worrying symptoms, contact NHS 111 through https://111.nhs.uk or by telephone before using the estimate.
Prompt
Calculate my estimated daily calorie needs using the Mifflin-St Jeor equation and show every step of the arithmetic. Use these details only: age [age], sex used by the equation [sex], height [height and unit], weight [weight and unit], usual activity [sedentary, lightly active, moderately active, very active, or extra active], and goal [maintain weight, lose weight, or gain weight]. Convert units transparently if needed. Give a maintenance estimate as a range, state the activity assumption behind it, and give any goal adjustment separately without presenting it as a guaranteed result. Do not diagnose me, prescribe a diet, or invent missing information. Ask for any missing input before calculating. Flag that this is an estimate, not medical care. If I am under 18, pregnant, breastfeeding, have a medical condition, take medication affected by food or weight, have a history of an eating disorder, or have worrying symptoms, do not set a calorie target and tell me to speak to a GP or another qualified health professional; for urgent or worrying symptoms direct me to NHS 111.
Open it prefilled in ChatGPT or Claude, or copy it into Gemini, which takes no prefill link.
Use a tool built for this
The distant third
What it gets wrong
- AI cannot know whether your reported activity level reflects your real routine, so the maintenance estimate can be based on the wrong multiplier.
- AI cannot account safely for every medical condition, medication, pregnancy, breastfeeding situation or eating-disorder history.
- AI cannot tell from a calorie calculation whether losing or gaining weight is appropriate for you.
- AI cannot replace a dietitian or clinician when your weight, appetite, symptoms or health needs are changing.
- The arithmetic is checkable, but the decision to act on the number remains yours.
Even on a YES, the friction has a name: judgement under ambiguity, verification cost and stakes of error.
How we scored this
Five axes, each scored nought to two by hand: ten means AI carries the task cleanly, and the thresholds that turn a total into YES, PARTLY or NO are published in the methodology. Each axis name links to its definition.
| Axis | Score (0–2) |
|---|---|
| Output | 2 |
| Inputs | 2 |
| Verification | 1 |
| Liability | 1 |
| Effort delta | 2 |
| Total | 8 / 10 |
The methodology and its thresholds are published in full.
FAQ
- Can ChatGPT work out how many calories I need a day?
- Yes. It can use your age, height, weight, sex used by the equation and activity level to produce an estimated maintenance range and show the arithmetic. It cannot tell whether that target is medically suitable for you.
- What information do I need to calculate my daily calories?
- Give the chatbot your age, height, current weight, sex used by the equation, usual activity level and whether you want to maintain, lose or gain weight. Keep your units clear and describe your normal activity rather than an unusually active day.
- Can AI tell me how many calories to eat to lose weight?
- It can apply a requested adjustment to an estimated maintenance figure, but the result is not a guaranteed or medically personalised target. Do not use an AI target without professional advice if you are under 18, pregnant, breastfeeding, have a relevant medical condition, take affected medication or have an eating-disorder history.
- Is an AI calorie calculation safe to use?
- It is reasonable as a rough planning estimate when your circumstances are straightforward and you check the inputs and arithmetic. Stop relying on it and speak to a GP or qualified health professional if you have worrying symptoms, and contact NHS 111 for urgent or worrying symptoms.
Nearby answers
Assessed by gpt-5.6-luna (gpt-5.6-luna) on 2026-08-13, second-checked by an independent model. Wrong somewhere? Email [email protected] and it gets re-checked.
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