How Many Calories Does Your Body Actually Need?
Search “how many calories should I eat” and you will drown in conflicting answers. The Estimated Energy Requirement (EER) cuts through the noise: it is the average daily energy intake predicted to maintain energy balance for a healthy person of your age, sex, weight, height and activity level.
The equations come from the Institute of Medicine’s Dietary Reference Intakes — the same formulas used in clinical nutrition and government dietary guidelines. This calculator implements the full IOM set: adults, children aged 3–18, plus the energy costs of pregnancy and lactation.
Estimated Energy Requirement · Institute of Medicine
? What is EER, and how is it different from TDEE?
EER (Estimated Energy Requirement) is the average daily energy intake predicted to maintain energy balance in a healthy person of a defined age, sex, weight, height and activity level. The equations come from the Institute of Medicine’s Dietary Reference Intakes.
TDEE and “maintenance calories” describe the same idea in fitness and dieting contexts. EER is the clinical/research term; the numbers are functionally equivalent when the inputs match.
Children use different equations (plus a growth energy deposit), and pregnancy/lactation add fixed energy costs on top of the non-pregnant value.
Please check your entries: age 3\u2013100, weight and height within realistic ranges.
An estimate for healthy, normal-weight individuals — not medical advice. The equations assume stable weight; illness, medication, extreme training or body-composition extremes change real needs. Children’s equations include the IOM growth deposit (+20/25 kcal). If you are pregnant, managing a condition, or an athlete, confirm targets with a qualified professional.
How to Use the EER Calculator
- Select sex and enter age — the equations differ by sex, and children use separate formulas.
- Enter weight and height (metric or imperial — the calculator converts).
- Pick your activity level honestly: sedentary, low active, active or very active. This sets the PA coefficient.
- Choose physiological state if applicable (pregnancy trimester or lactation stage adds the IOM energy cost).
- Click Calculate My EER to see your daily calorie target with the full working shown.
The IOM EER Formulas
Men: EER = 662 − 9.53×A + PA×(15.91×W + 539.6×H)
Women: EER = 354 − 6.91×A + PA×(9.36×W + 726×H)
Children 9–18: boys 88.5 − 61.9×A + PA×(26.7×W + 903×H) + 25 | girls 135.3 − 30.8×A + PA×(10.0×W + 934×H) + 25
A = age (yrs), W = weight (kg), H = height (m), PA = activity coefficient
Worked example: 30-year-old man, 80 kg, 1.80 m, active (PA = 1.25). EER = 662 − 9.53×30 + 1.25×(15.91×80 + 539.6×1.80) = 662 − 285.9 + 1.25×2244.1 = 3,181 kcal/day.
Pregnancy/lactation additions: 2nd trimester +340, 3rd trimester +452, lactation 0–6 mo +330, 7–12 mo +400 kcal/day.
Worked example: a woman with a desk job and evening walks
A 28-year-old woman, 65 kg, 1.65 m tall, is low active (PA = 1.12). EER = 354 − 6.91×28 + 1.12×(9.36×65 + 726×1.65) = 354 − 193.5 + 1.12×1,806.3 = 2,184 kcal/day. Same stats but sedentary (PA = 1.00) drops the answer to about 1,967 kcal/day — a reminder that the activity choice alone can swing the estimate by over 200 kcal.
Worked example: a child
A 10-year-old boy, 35 kg, 1.40 m tall, is active (PA = 1.26). Using the boys 9–18 equation: EER = 88.5 − 61.9×10 + 1.26×(26.7×35 + 903×1.40) + 25 = 88.5 − 619 + 2,770.4 + 25 = 2,265 kcal/day. The final +25 is the growth deposit — energy set aside for building new tissue, which is why children’s equations end with +20 (ages 3–8) or +25 (ages 9–18) rather than zero.
PA Coefficients by Group
| Activity level | Adult men | Adult women | Boys 3–18 | Girls 3–18 |
|---|---|---|---|---|
| Sedentary | 1.00 | 1.00 | 1.00 | 1.00 |
| Low active | 1.11 | 1.12 | 1.13 | 1.16 |
| Active | 1.25 | 1.27 | 1.26 | 1.31 |
| Very active | 1.48 | 1.45 | 1.42 | 1.56 |
Which Activity Level Are You, Really?
Most EER mistakes are made here, not in the arithmetic. The IOM categories describe your whole day, not your best workout: Sedentary (PA 1.00) means a desk-based day with under ~5,000 steps and no regular exercise. Low active means roughly 5,000–7,500 steps or light exercise a few times a week. Active means a mostly on-your-feet day, 7,500–10,000+ steps, or structured training most days. Very active is reserved for physical jobs (construction, farming, professional sport) or hard daily training — a small minority. When torn between two levels, pick the lower one: people systematically overestimate their activity, and an honest PA choice is worth more accuracy than any other single input.
Turning Your EER Into a Weight Plan
Your EER is the maintenance anchor — the budget at which your weight should hold steady. To change weight, shift the budget deliberately:
- Losing: eat roughly 300–500 kcal/day below your EER for a loss of about 0.3–0.45 kg (roughly 0.5–1 lb) per week. Larger deficits are rarely sustainable and, for smaller adults, should never push intake below about 1,200 kcal/day (women) or 1,500 kcal/day (men) without medical supervision.
- Gaining: add 250–500 kcal/day above your EER, paired with resistance training if the goal is muscle rather than simply mass.
- Maintaining: stay within about ±100 kcal of your EER and let the weekly average, not any single day, be the judge.
Whichever direction you choose, treat the equation’s output as a first draft. Track your weight trend for two to three weeks at a consistent intake: if the trend is flat when you wanted a loss, trim another 100–200 kcal; if you are losing faster than planned, add some back. Doubly labelled water studies — the research behind these formulas — show the equations predict group averages very well, but any individual’s true expenditure can differ by a few hundred calories, and your own data is the correction.
EER vs. TDEE vs. Maintenance Calories
Different names, same destination. EER is the clinical and research term (dietary guidelines, hospitals, studies). TDEE (total daily energy expenditure) is the fitness-community term. Maintenance calories is the dieting-world term. All three estimate the calories needed to hold current weight — this calculator gives you the IOM-grade version of that number.
Use your EER as the anchor: eat near it to maintain, below it to lose, above it to gain. Adjust after 2–3 weeks of real-world results, because no equation beats your own data.
Frequently Asked Questions
What is EER in nutrition?
Estimated Energy Requirement (EER) is the average daily energy intake predicted to maintain energy balance in a healthy person of a defined age, sex, weight, height and activity level, using Institute of Medicine equations.
How is EER different from TDEE?
They describe the same concept — daily calories to maintain weight. EER is the clinical/research term from dietary guidelines; TDEE is the fitness-community term. The numbers are functionally equivalent when inputs match.
How do you calculate EER for adults?
For men 19+: EER = 662 − 9.53×age + PA×(15.91×weight_kg + 539.6×height_m). For women 19+: EER = 354 − 6.91×age + PA×(9.36×weight_kg + 726×height_m), where PA is the activity coefficient (1.00–1.48).
What is the EER during pregnancy?
The IOM adds energy costs on top of the non-pregnant EER: +0 in the 1st trimester, +340 kcal/day in the 2nd, +452 in the 3rd; lactation adds +330 (0–6 months) or +400 (7–12 months).
Can children use the EER calculator?
Yes — the IOM publishes separate equations for ages 3–18 with different coefficients plus a small growth energy deposit (+20 or +25 kcal/day). This calculator applies them automatically by age.
Why does activity level change EER so much?
The PA coefficient multiplies the weight-and-height term, so moving from sedentary (1.00) to very active (1.48) can add 800+ kcal/day for the same person. Honest activity selection is the biggest accuracy lever.
How accurate is an EER estimate?
The IOM equations were built from doubly labelled water measurements and predict average needs for groups very well. For an individual, expect the true figure to be within roughly 10% either way, because metabolism, body composition and unlogged movement vary. Use your EER as the starting point, track your weight for two to three weeks, and adjust by 100–200 kcal based on the trend.
Does this calculator cover babies and toddlers under 3?
No. The IOM publishes separate infant and toddler equations (based on 89 × weight in kg − 100, plus an age-specific energy deposit), but very young children’s needs should come from their paediatrician and growth charts, not a general calculator. This tool implements the IOM equations for ages 3 and up, plus adults.
Final Thoughts
Your EER is the single most useful number in nutrition planning — the anchor every deficit, surplus and maintenance phase hangs from. Calculate it with the clinical equations above, run it against 2–3 weeks of real results, and adjust. That loop beats any one-size-fits-all calorie chart.
Got Your EER? Build the Full Plan
Turn it into meals with our macro calculator and calorie calculator.