· Updated · By Kaunto
How Many Calories Should I Eat a Day? The Equation, the Tables and How to Adjust
Most adults maintain on 1,800–2,800 kcal a day. Here is how to estimate yours with the Mifflin–St Jeor equation, what to add or subtract for a goal, and how to correct it after two weeks.
Most adults maintain their weight on somewhere between 1,800 and 2,800 kcal a day, and the number for you depends mainly on your weight, height, age, sex and how much you move. The most reliable way to estimate it without lab equipment is the Mifflin–St Jeor equation for resting energy, multiplied by an activity factor of 1.2 to 1.9. To lose fat, eat 15–25 % below that; to gain muscle, 5–15 % above. The macro calculator does the arithmetic with the Kaunto app’s own formula, which uses a more conservative activity scale and a deficit set by weekly pace; this article explains the classic method so you can sanity-check any result and adjust it once your log tells you what your body actually does.
Step 1: resting energy
Resting (basal) energy is what you burn lying still: roughly 60–70 % of a typical day’s total. The Mifflin–St Jeor equation, published in 1990 and validated against measured metabolic rate more often than the older Harris–Benedict, is:
| Equation | |
|---|---|
| Men | 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 |
| Women | 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161 |
A 75 kg, 175 cm, 30-year-old man: 750 + 1,094 − 150 + 5 = 1,699 kcal. A 60 kg, 163 cm, 40-year-old woman: 600 + 1,019 − 200 − 161 = 1,258 kcal. The equation is accurate to within about 10 % for roughly two-thirds of people; it drifts most for people with much more or much less muscle than average for their weight.
Step 2: activity
Multiply resting energy by an activity factor. Almost everyone picks too high a factor, because the descriptions sound like less than they are:
| Factor | Label | What it actually means |
|---|---|---|
| 1.2 | Sedentary | Desk job, under 5,000 steps, no structured exercise |
| 1.375 | Light | 1–3 sessions a week, or an active day of walking |
| 1.55 | Moderate | 3–5 sessions a week of an hour, plus normal daily movement |
| 1.725 | Active | Hard training 6–7 days a week |
| 1.9 | Very active | Physical job plus daily training, or twice-a-day training |
Three gym sessions a week with a desk job is light, not moderate. The example man at 1.55 has a maintenance of 1,699 × 1.55 = 2,633 kcal; at 1.375 it is 2,336. That 300 kcal gap is the whole of a modest fat-loss deficit, which is why the activity factor matters more than the equation.
The macro calculator and the Kaunto app use a deliberately lower scale, 1.2, 1.3, 1.4, 1.5 and 1.65, because the classic factors assume an active baseline and read 200–350 kcal high for a desk job plus training. Expect its maintenance figure to sit below the table here.
Maintenance calories by weight
Computed with the same equation, for a 30-year-old of average height. Use the calculator for your own age and height.
| Weight | Sedentary | Light | Moderate | Active |
|---|---|---|---|---|
| Man, 175 cm, 65 kg | 1,919 | 2,198 | 2,478 | 2,758 |
| Man, 175 cm, 75 kg | 2,039 | 2,336 | 2,633 | 2,930 |
| Man, 175 cm, 85 kg | 2,159 | 2,473 | 2,788 | 3,103 |
| Woman, 163 cm, 55 kg | 1,509 | 1,729 | 1,950 | 2,170 |
| Woman, 163 cm, 65 kg | 1,629 | 1,867 | 2,105 | 2,342 |
| Woman, 163 cm, 75 kg | 1,749 | 2,004 | 2,260 | 2,515 |
Step 3: the goal
| Goal | Adjustment | Expected change | Why not more |
|---|---|---|---|
| Lose fat | −15 to −25 % (typically 300–600 kcal) | Roughly 0.25–0.5 kg a week | Larger deficits cost muscle, training quality and adherence |
| Maintain | 0 | Weight stable within ±1 kg | |
| Gain muscle | +5 to +15 % (typically 150–350 kcal) | Roughly 0.1–0.25 kg a week | Beyond that the surplus is stored as fat, not muscle |
A kilogram of body fat holds about 7,700 kcal, so a 500 kcal daily deficit predicts about 0.45 kg a week. Real losses are slower than the arithmetic after the first weeks, because a lighter body burns less and because activity tends to fall in a deficit. That is normal and is why the number gets adjusted rather than set once.
Step 4: adjust from what actually happens
The equation gives a starting point; the log and the scale give the truth. After two to three weeks of consistent logging:
- Average the daily intake over the whole period, including weekends.
- Compare the weight trend, using a weekly average rather than day-to-day readings, which swing 1–2 kg with water and food in transit.
- If the trend does not match the goal, move intake by 100–200 kcal and repeat. Do not change more than that at once; you are trying to find the number, not overshoot it.
Whatever the log says you eat at a stable weight is your maintenance in logged calories. Database and label errors are inside that number, which is why a consistently kept log works even though no individual entry is exact.
What the calories are made of
Once the total is set, the split matters for how the deficit feels and what you keep. Protein first, at 1.6–2.2 g per kg of bodyweight (how much protein per day); fat at 20–35 % of calories; carbohydrate takes the rest. For the 2,633 kcal example: 120 g protein, 73 g fat, 374 g carbohydrate. Seeing those in food helps: 374 g of carbohydrate is about three cups of cooked rice, two bananas, two slices of whole-wheat bread and a cup of oats, with room left. The split is covered in how to count macros.
Frequently asked questions
How many calories should I eat to lose weight? About 15–25 % below your maintenance, which for most adults lands between 1,400 and 2,200 kcal a day. Estimate maintenance with Mifflin–St Jeor and an honest activity factor, subtract 300–600 kcal, and adjust after two weeks based on the weight trend.
Is 1,200 calories a day enough? For most adults it is below what can comfortably supply protein, fibre and micronutrients, and below resting energy for many. It is the floor several health bodies use for supervised programmes, not a general target. A deficit of 15–25 % from a properly estimated maintenance is almost always higher than 1,200.
How accurate is the Mifflin–St Jeor equation? It predicts measured resting energy to within 10 % for about 70 % of adults, better than Harris–Benedict and about as well as any equation that needs no body-composition data. The activity multiplier adds more uncertainty than the equation itself.
Do I need to eat back exercise calories? Not if your activity factor already includes the training, which it should. Counting the workout again double-counts it. If a fitness tracker reports a session as 600 kcal, treat it as an overestimate; wrist devices commonly overstate exercise energy by 20–50 %.
Why has my weight stopped dropping on the same calories? Because you are lighter, so maintenance has fallen, and because non-exercise activity tends to decline in a deficit. Re-run the estimate at your new weight, or reduce intake by 100–150 kcal, and check the trend again after two weeks.
Next: set the split with the best macro split for cutting, or run your numbers in the macro calculator.