Where the numbers come from
Sources last reviewed: 18.08.2026 · Formula version: hapka-targets-2026-08
Hapka provides general nutrition information for healthy adults. It is not a medical device and does not diagnose, treat, or prevent any condition.
Do not use Hapka to make medical decisions. Consult a doctor before making medical decisions or before changing your calorie, protein, or fluid intake if you have a medical condition, symptoms, take medicines that affect nutrition or hydration, or have been prescribed a diet, protein limit, or fluid limit.
How to read this page
Each number used in Hapka's automatic calorie, protein, and water target calculations is either linked to a published source or explicitly identified as a Hapka-defined calculation rule or software guardrail. The sources fall into three kinds, and this page always says which:
• Official reference values - published by EFSA (EU) or WHO for healthy populations. They are references for groups, not individual prescriptions, and they do not automatically apply in illness.
• Research-based practical targets - from position stands and meta-analyses, used where the official reference value serves a different purpose than a personal goal. Protein is the main case.
• Hapka-defined rules - our own conservative choices, always marked as such. They explain how the app creates an editable starting target. They are not clinical standards, medical prescriptions, safety guarantees, or claims that the resulting target is appropriate for every individual.
Calories
Resting energy is estimated with the Mifflin-St Jeor equation [1] from the sex, age, height and weight you enter, then multiplied by an activity factor [3] to estimate what you burn across a day. It is an estimate and may differ materially from an individual's measured energy expenditure; in a systematic review of predictive equations it was the most reliable of the common formulas, while still missing by more than 10% for a meaningful share of people [2].
Hapka-defined rules: the deficit never exceeds 25% of your estimated daily burn; the surplus never exceeds the smaller of 500 kcal and 10%; a target never falls below 1200 kcal (female formula) or 1500 kcal (male formula); and results are rounded to 50 kcal, because an approximate formula should not display false precision.
- [1] Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 1990;51(2):241-247
- [2] Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc 2005;105(5):775-789
- [3] EFSA - Dietary Reference Values (energy, and physical activity levels)
Protein
EFSA's Population Reference Intake (PRI) for healthy adults is 0.83 g per kg of body weight per day [1]. A PRI is intended to meet the needs of almost all healthy people in a population group; it is not a personalized minimum, an exercise target, or a medical prescription. For people who train, Hapka uses practical targets from inside the published ranges: about 1.4-2.0 g/kg is the range commonly cited for people who train regularly [2]; a meta-analysis of adults undertaking resistance training found the additional benefit for gains in fat-free mass levelling off at approximately 1.6 g/kg/day - not a general upper limit or a recommendation for every adult [3]; and 1.0-1.2 g/kg is the range widely recommended from age 65 [4].
Hapka-defined rules: a coefficient between 1.0 and 1.6 g/kg chosen by your goal and activity level; a calculation weight capped at the weight for BMI 30, so a very high body weight cannot multiply into an extreme target; and a ceiling of 35% of your calories, which matches the top of the acceptable macronutrient distribution range for protein (10-35% of energy) published by the U.S. National Academies [5] - Hapka uses it as a composition guardrail, not an individual safety threshold. EFSA did not establish a tolerable upper intake level for protein because the available evidence was insufficient; that should not be read as meaning unlimited protein intake is safe.
- [1] EFSA - Scientific Opinion on Dietary Reference Values for protein (2012): PRI 0.83 g/kg per day
- [2] Jäger R, et al. ISSN Position Stand: protein and exercise. J Int Soc Sports Nutr 2017;14:20
- [3] Morton RW, et al. Systematic review, meta-analysis and meta-regression of protein supplementation and resistance training. Br J Sports Med 2018;52(6):376-384
- [4] Bauer J, et al. Evidence-based recommendations for optimal dietary protein intake in older people (PROT-AGE). J Am Med Dir Assoc 2013;14(8):542-559
- [5] Institute of Medicine / National Academies - Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (2005)
Water
EFSA's adequate-intake values are about 2.0 L a day for women and about 2.5 L for men in a temperate climate, and they refer to TOTAL water from food and all drinks - not to plain water alone [1].
Hapka-defined rule: the water goal is a starting habit target for the plain water you drink. The 30-37 ml/kg calculation (on the same BMI-30 calculation weight) and the 1.5-3.0 L range are app-defined reminder defaults; the resulting goal is editable. They are not EFSA reference values, physiological requirements, medical hydration prescriptions, or safety thresholds. Water from food and other non-alcoholic drinks also contributes to hydration, and the goal can be edited or turned off. If you have a fluid restriction, follow the target your doctor set.
What calories and protein do not tell you
Hitting a calorie and protein target does not by itself mean a diet is balanced or complete. WHO's healthy-diet guidance covers what this kind of tracking cannot: at least 400 g of fruit and vegetables a day, free sugars under 10% of energy, saturated fat under 10%, and salt under 5 g a day [1].
When Hapka suggests no targets at all
Automatic calorie, protein, and water targets are switched off - while manual logging stays fully available - if you are under 18, pregnant or breastfeeding, have a history of disordered eating, follow a prescribed diet or a protein/fluid restriction, or when your BMI is below 16 (for any goal) or below 18.5 for a weight-loss goal. BMI is body weight in kilograms divided by the square of height in meters [1]; these cut-offs are Hapka's conservative gates. In those situations the targets belong to a doctor or a qualified nutrition professional, not to a formula.