Bo guide
Short answer
Most adults need between 1,600 and 3,000 calories a day. Women average around 2,000 and men around 2,500, adjusted for age, size and activity level.
General information, not medical advice. Written from published sources, which are listed at the end. It is not a substitute for a doctor, pharmacist or registered dietitian who knows your situation.
In this guide10 sections · 4 min
Most adults need somewhere between 1,600 and 3,000 calories a day. As a rough midpoint, women average around 2,000 and men around 2,500 — but the spread is wide, and the averages are not a target.
What moves your number
- Size. More body mass costs more energy to maintain, including muscle mass.
- Activity. The single biggest variable between two similar people. A desk job and a physical job can differ by 500+ calories a day.
- Age. Requirements decline gradually through adulthood.
- Sex. Largely a proxy for average body size and composition.
- Health status. Pregnancy, breastfeeding, thyroid conditions and some medications all shift the number.
Working out your own number
Averages are a starting point, not a target. The standard way to estimate your own is the Mifflin-St Jeor equation, which gives your resting metabolic rate — what you burn doing nothing at all:
- Men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
- Women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
Then multiply by an activity factor to get your total daily burn:
| Activity level | Multiply by | Roughly means |
|---|---|---|
| Sedentary | 1.2 | Desk job, little deliberate exercise |
| Lightly active | 1.375 | Light exercise 1–3 days a week |
| Moderately active | 1.55 | Moderate exercise 3–5 days a week |
| Very active | 1.725 | Hard exercise 6–7 days a week |
| Extremely active | 1.9 | Physical job, or twice-daily training |
A worked example
A 32-year-old woman, 68 kg, 168 cm, who trains three times a week:
- Resting rate: (10 × 68) + (6.25 × 168) − (5 × 32) − 161 = 1,409 calories
- Moderately active, so × 1.55 = 2,184 calories maintenance
- For fat loss, subtract 400: ~1,780 calories a day
Where the formula is wrong
Treat the result as a hypothesis, not a fact. The activity multipliers are broad brackets, and the biggest individual variable — NEAT, the energy you spend fidgeting, walking and standing — varies by several hundred calories a day between two people who look identical on paper.
The formula gets you a sensible starting point. Two to three weeks of measuring what actually happens gets you the real number, which is why finding your maintenance by observation beats any equation.
Typical ranges, for a sanity check
If the arithmetic above produced something that feels wrong, compare it against the general pattern before trusting it:
| Sedentary | Moderately active | Very active | |
|---|---|---|---|
| Women, 19–30 | ~1,800–2,000 | ~2,000–2,200 | ~2,400 |
| Women, 31–50 | ~1,800 | ~2,000 | ~2,200 |
| Women, 51+ | ~1,600 | ~1,800 | ~2,000–2,200 |
| Men, 19–30 | ~2,400–2,600 | ~2,600–2,800 | ~3,000 |
| Men, 31–50 | ~2,200–2,400 | ~2,400–2,600 | ~2,800–3,000 |
| Men, 51+ | ~2,000–2,200 | ~2,200–2,400 | ~2,400–2,800 |
These are population averages for weight maintenance, not targets. If your calculated number sits far outside the relevant row, check the activity multiplier first — over-rating your own activity level is the most common way people get an inflated figure.
Should you eat back exercise calories?
Generally not, or only part of them, for two reasons that compound.
The first is that calorie burn from wearables and gym machines is routinely overstated, sometimes substantially. The second is that if you used an activity multiplier above, your exercise is already counted — adding the workout again on top double-counts it.
The cleaner method is to pick a single number that includes your usual training, eat it on every day, and judge it by what the scale does over three weeks. If your training genuinely varies a great deal week to week, eating back roughly half of the estimated burn is a reasonable compromise.
If you want to lose weight
A deficit of roughly 500 calories a day produces about 1 pound of weight loss per week. That is the standard, sustainable starting point — and the reason 1,200 calories is too low for most people.
Larger deficits are not proportionally better. They are harder to hold, tend to cost more muscle, and the fast early drop is substantially water weight, which returns.
Why your number is not fixed
Calorie needs fluctuate. They shift with weight — a lighter body burns less — and with activity, sleep and even ambient temperature. A number that worked at the start of a cut will not be right ten pounds later.
This is why tracking the trend over weeks beats obsessing over a single day. One high day is noise; three flat weeks is information.
A practical approach
- Estimate a starting number from a calculator, or start by simply logging what you currently eat for a week.
- Hold it for two to three weeks and track weight as a weekly average, not daily.
- Adjust by 200–300 calories based on what actually happened, not what should have happened.
- Repeat. This beats any formula because it is measured on you.
Situations where this does not apply
- Pregnancy and breastfeeding. Requirements rise, and a deficit is not appropriate without medical guidance.
- Older adults. Needs fall, but protein requirements do not — under-eating here costs muscle quickly.
- Teenagers and adolescents. Still growing; calorie restriction should involve a doctor.
- Endurance athletes. Standard multipliers understate high-volume training badly.
- Thyroid conditions, diabetes, and some medications. All shift the number enough to be worth a conversation.
