# Calorie and macro calculator

> Daily calorie target for losing, maintaining or gaining weight, with macros in grams of protein, carbohydrate and fat per day and per meal.

Interactive version: https://www.calcopenly.com/health/calorie-macro-calculator
Subject: Health and fitness calculators

The calculation starts from maintenance calories (TDEE), the Mifflin-St Jeor BMR times an activity factor. For a weight-change goal it adds or subtracts the weekly rate × 7,700 kcal per kg ÷ 7 days. The target is then split into protein, carbohydrate and fat with the Atwater factors of 4, 4 and 9 kcal per gram, and divided across your meals.

People use it to turn a goal such as losing 0.5 kg a week into daily numbers. For the default 30-year-old man (70 kg, 175 cm, moderately active), maintenance is 2,556 kcal, a 550 kcal deficit gives a 2,006 kcal target, and the balanced split is 100 g protein, 251 g carbohydrate and 67 g fat.

The 7,700 kcal per kg rule is static: energy needs fall as weight drops, so real loss slows over time (Hall et al., 2011). Splits outside the US Acceptable Macronutrient Distribution Ranges, which are population ranges, are flagged.

## How the daily calorie target is worked out

The calculator runs four steps. Here they are for a 40-year-old woman who weighs 80 kg, is 165 cm tall, is lightly active and wants to lose 0.5 kg a week on the balanced split with three meals:

1. Resting energy by Mifflin-St Jeor: 10 × 80 + 6.25 × 165 − 5 × 40 − 161 = 1,470.25 kcal.
2. Maintenance (TDEE): 1,470.25 × 1.375 for light activity = 2,021.6 kcal.
3. Daily deficit: 0.5 kg × 7,700 kcal ÷ 7 days = 550 kcal, so the target is 2,021.6 − 550 = 1,471.6, shown as 1,472 kcal.
4. Macros: 20 % of 1,471.6 is 294.3 kcal of protein, or 74 g at 4 kcal per gram; 50 % is 184 g of carbohydrate; 30 % is 441.5 kcal of fat, or 49 g at 9 kcal per gram. Each of the three meals gets 491 kcal and 25 g of protein.

The calculator carries full precision through every step and rounds only the displayed figures. The [BMR and TDEE calculator](/health/bmr-tdee-calculator) shows the first two steps with the Harris-Benedict and Katch-McArdle equations beside Mifflin-St Jeor, so you can see how much the starting number depends on the equation.

## Calorie deficit and expected rate of weight loss

Each rate you pick becomes a fixed daily deficit. The table uses the same woman, whose maintenance is 2,022 kcal a day.

| Loss per week | Daily deficit | Daily target | Deficit as share of maintenance |
|---|---|---|---|
| 0.25 kg | 275 kcal | 1,747 kcal | 13.6 % |
| 0.5 kg | 550 kcal | 1,472 kcal | 27.2 % |
| 0.75 kg | 825 kcal | 1,197 kcal | 40.8 % |
| 1 kg | 1,100 kcal | 922 kcal | 54.4 % |
| 1 lb (0.454 kg) | 499 kcal | 1,523 kcal | 24.7 % |
| 2 lb (0.907 kg) | 998 kcal | 1,024 kcal | 49.4 % |

The [NHLBI practical guide](https://www.nhlbi.nih.gov/files/docs/guidelines/prctgd_c.pdf) on adult obesity sets the rate at 1 to 2 lb a week and notes that faster loss does not give better long-term results. The [NHS](https://www.nhs.uk/live-well/healthy-weight/managing-your-weight/tips-to-help-you-lose-weight/) gives the same range as 0.5 to 1 kg a week. A fixed deficit is a much larger bite out of a small person's intake: 1 kg a week takes more than half of this woman's maintenance, and its 922 kcal target sets off the calculator's warning for women below 1,000 kcal.

Expect the real curve to flatten. In [Hall and colleagues' 2011 model](https://pmc.ncbi.nlm.nih.gov/articles/PMC3880593/), a sedentary 100 kg man who cuts 480 kcal a day levels off near 75 kg, reaching half of that loss in about a year and 95 % in about three years. Hall's team calculated that the static rule, which the calculator uses, predicts 22 kg lost in the first year for the same cut, about twice what their model predicts. Treat the target as a starting point and recalculate as your weight changes.

## Protein targets by goal

Protein needs scale with body weight, not with calories. These are the published figures in grams per kilogram of body weight per day:

| Situation | Protein (g/kg/day) | Source |
|---|---|---|
| RDA for healthy adults | 0.8 | [Institute of Medicine, 2005](https://nap.nationalacademies.org/catalog/10490) |
| Exercising adults building or keeping muscle | 1.4 to 2.0 | [ISSN position stand, 2017](https://doi.org/10.1186/s12970-017-0177-8) |
| Resistance training for muscle gain | about 1.6, up to 2.2 | [Morton et al., 2018](https://pmc.ncbi.nlm.nih.gov/articles/PMC5867436/) |
| Lean, resistance-trained, in a deficit | 2.3 to 3.1 per kg of fat-free mass | [Helms et al., 2014](https://pubmed.ncbi.nlm.nih.gov/24092765/) |

Morton's meta-analysis of 49 trials found no further gain in fat-free mass from resistance training above a total protein intake of about 1.62 g/kg a day. The 95 % confidence interval ran to 2.2 g/kg, which the authors suggested for people aiming for the largest gain. Helms's range is per kilogram of lean mass, which the [body fat calculator](/health/body-fat-calculator) estimates.

Because the macro split is a share of calories, the grams of protein fall as the deficit grows. Check the "Protein per kg of body weight" output against the table. For a figure set from body weight alone, use the [protein intake calculator](/health/protein-intake-calculator) and build the rest of the day around it.

## Macro split presets compared

On the woman's 1,472 kcal target, the four presets give:

| Preset (protein / carbs / fat) | Protein | Carbohydrate | Fat | Protein per kg |
|---|---|---|---|---|
| Balanced (20 / 50 / 30) | 74 g | 184 g | 49 g | 0.92 g/kg |
| Low-carb (30 / 20 / 50) | 110 g | 74 g | 82 g | 1.38 g/kg |
| High-protein (40 / 30 / 30) | 147 g | 110 g | 49 g | 1.84 g/kg |
| Keto (20 / 5 / 75) | 74 g | 18 g | 123 g | 0.92 g/kg |

The balanced preset, the only one inside the US Acceptable Macronutrient Distribution Ranges, leaves this dieter just above the RDA for protein. The high-protein preset clears the 1.6 g/kg level from Morton's analysis. The same percentage gives more grams on a larger budget: a 20 % protein share is 150 g at 3,000 kcal but 75 g at 1,500 kcal.

## Minimum calorie intake and when to get supervision

The calculator warns when the target falls below 1,000 kcal a day for women or 1,200 for men. Those are the lower ends of the low-calorie diet ranges in the NHLBI guide: 1,000 to 1,200 kcal a day for most women, and 1,200 to 1,600 for men and for women who weigh 165 lb or more or exercise regularly. The guide calls diets under 800 kcal a day very-low-calorie diets, which need special monitoring and should not be used routinely.

UK guidance is stricter. [NICE guideline NG246](https://www.nice.org.uk/guidance/ng246/chapter/Physical-activity-and-diet) (2025) recommends low-energy diets of 800 to 1,200 kcal a day only as part of a specialist weight management service with long-term support, and diets under 800 kcal only when there is a clinically assessed need to lose weight fast, such as before surgery.

The calculator also flags any rate above 1 kg a week and refuses a rate whose deficit is as large as your whole maintenance intake. It accepts ages from 18 and has no adjustment for pregnancy or breastfeeding.

## Mistakes that throw the numbers off

- **Counting exercise twice.** The activity level already includes your training. Adding the calories from a [calories burned calculator](/health/calories-burned-calculator) on top of the moderately active factor counts the same sessions again.
- **Keeping an old target.** Every kilogram lost lowers Mifflin-St Jeor by 10 kcal. For the woman above, 5 kg down cuts maintenance by 50 × 1.375 = 69 kcal a day, so the same target now gives a 619 kcal deficit instead of 550.
- **Mixing up units.** A rate of 1 in pounds is a 499 kcal deficit; the same 1 in kilograms is 1,100 kcal. Check the unit beside the rate field.
- **Custom shares that miss 100 %.** The calculator will not split calories until protein, carbohydrate and fat add up to exactly 100 %.
- **Judging the plan by a single weigh-in.** Compare averages over two or three weeks before you change the target.

## Inputs

- **Sex (for the formula)** (options: Male, Female)
- **Age**
- **Weight**
- **Height**: Accepts 5'11" or 5 ft 11 in
- **Activity level** (options: Sedentary (×1.2), Lightly active (×1.375), Moderately active (×1.55), Very active (×1.725), Extra active (×1.9))
- **Goal** (options: Lose, Maintain, Gain)
- **Change per week**
- **Macro split** (options: Balanced, Low-carb, High-protein, Keto, Custom)
- **Protein share**
- **Carbohydrate share**
- **Fat share**
- **Meals per day**

## Results

- Daily calorie target (kcal/day) — main result
- Maintenance calories (TDEE) (kcal/day)
- Daily deficit (−) or surplus (+) (kcal/day)
- Protein (g/day)
- Carbohydrate (g/day)
- Fat (g/day)
- Calories per meal (kcal)
- Protein per meal (g)
- Protein per kg of body weight (g/kg)

## Formula

$$
\text{target} = \text{TDEE} \pm \frac{\text{rate (kg/week)} \times 7700}{7},\qquad \text{grams} = \frac{\text{target} \times \text{share}}{4\ \text{(protein, carbs)}\ \text{or}\ 9\ \text{(fat)}}
$$

## Worked examples

### Maintain, balanced split, 3 meals

- Sex (for the formula): Male
- Age: 30 years
- Weight: 70 kg
- Height: 175 cm
- Activity level: Moderately active (×1.55)
- Goal: Maintain
- Macro split: Balanced
- Meals per day: 3
- **Daily calorie target: 2,556 kcal/day**
- **Protein: 128 g/day**
- **Carbohydrate: 319 g/day**
- **Fat: 85 g/day**
- **Calories per meal: 852 kcal**
- Checked against: Python 3.8 decimal: Mifflin 1648.75 × 1.55 = 2555.5625; 20 %/4, 50 %/4, 30 %/9 → 127.778, 319.445, 85.185 g; ÷ 3 meals

### Lose 0.5 kg a week, high-protein, 4 meals

- Sex (for the formula): Female
- Age: 35 years
- Weight: 70 kg
- Height: 168 cm
- Activity level: Lightly active (×1.375)
- Goal: Lose
- Change per week: 0.5 kg
- Macro split: High-protein
- Meals per day: 4
- **Maintenance calories (TDEE): 1,944 kcal/day**
- **Daily deficit (−) or surplus (+): -550 kcal/day**
- **Daily calorie target: 1,394 kcal/day**
- **Protein: 139 g/day**
- **Carbohydrate: 105 g/day**
- **Fat: 46 g/day**
- **Calories per meal: 349 kcal**
- Checked against: Python 3.8 decimal: Mifflin 1414 × 1.375 = 1944.25; 0.5 × 7700 / 7 = 550; 40/30/30 split at 4/4/9 kcal per g

### Gain 0.5 lb a week on keto

- Sex (for the formula): Male
- Age: 25 years
- Weight: 80 kg
- Height: 180 cm
- Activity level: Very active (×1.725)
- Goal: Gain
- Change per week: 0.5 lb
- Macro split: Keto
- Meals per day: 3
- **Daily deficit (−) or surplus (+): 249 kcal/day**
- **Daily calorie target: 3,363 kcal/day**
- **Protein: 168 g/day**
- **Carbohydrate: 42 g/day**
- **Fat: 280 g/day**
- Checked against: Python 3.8 decimal: 0.5 lb = 0.226796185 kg × 7700 / 7 = 249.4758035; Mifflin 1805 × 1.725 = 3113.625; 20/5/75 split

### Zero rate with a custom split

- Sex (for the formula): Female
- Age: 28 years
- Weight: 55 kg
- Height: 160 cm
- Activity level: Moderately active (×1.55)
- Goal: Lose
- Change per week: 0 kg
- Macro split: Custom
- Protein share: 30%
- Carbohydrate share: 40%
- Fat share: 30%
- Meals per day: 5
- **Daily calorie target: 1,936 kcal/day**
- **Daily deficit (−) or surplus (+): 0 kcal/day**
- **Protein: 145 g/day**
- **Carbohydrate: 194 g/day**
- **Fat: 65 g/day**
- **Protein per meal: 29 g**
- Checked against: Python 3.8 decimal: Mifflin 1249 × 1.55 = 1935.95 with no deficit; 30/40/30 split; ÷ 5 meals

## Questions

### What calorie deficit loses 0.5 kg a week?

About 550 kcal a day by the usual rule of 7,700 kcal per kg (3,500 kcal per pound, from Wishnofsky 1958): 0.5 × 7,700 ÷ 7 = 550. The NHLBI adult obesity guidance pairs a deficit of 500 to 1,000 kcal a day with a loss of 1 to 2 lb (0.45 to 0.9 kg) a week. Measured loss usually slows after the first weeks because energy needs fall as weight drops.

### Why does weight loss slow down on the same calories?

A smaller body uses less energy, so a fixed intake produces a shrinking deficit. Hall and colleagues' 2011 model in The Lancet found that the body weight response to a change in intake has a half-time of about a year; for an average overweight adult, each 100 kJ (24 kcal) a day cut from intake eventually lowers weight by about 1 kg. The static 7,700 kcal per kg rule ignores this and overstates long-term loss.

### What macro split is recommended for adults?

The US Dietary Reference Intakes set Acceptable Macronutrient Distribution Ranges of 10–35 % of energy from protein, 45–65 % from carbohydrate and 20–35 % from fat, ranges linked with lower chronic disease risk while meeting nutrient needs. The balanced preset here (20/50/30) sits inside all three. The high-protein, low-carb and keto presets fall outside the carbohydrate range and are flagged.

### How do you convert calories into grams of protein, carbs and fat?

Divide the calories from each macronutrient by its Atwater factor: 4 kcal per gram for protein and carbohydrate and 9 for fat (alcohol is 7), the general factors listed by FAO. On a 2,006 kcal target split 20/50/30, that is 401 ÷ 4 = 100 g protein, 1,003 ÷ 4 = 251 g carbohydrate and 602 ÷ 9 = 67 g fat.

### How accurate is the calorie and macro calculator?

Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 4 worked examples whose answers come from independent sources; for example, “Maintain, balanced split, 3 meals” is checked against Python 3.8 decimal: Mifflin 1648.75 × 1.55 = 2555.5625; 20 %/4, 50 %/4, 30 %/9 → 127.778, 319.445, 85.185 g; ÷ 3 meals.

### Where does the method come from?

Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (2005) — AMDR; FAO. Food energy — methods of analysis and conversion factors (Food and Nutrition Paper 77, 2003) — Atwater general factors; Wishnofsky M. Caloric equivalents of gained or lost weight. Am J Clin Nutr 1958;6:542–546; Hall KD et al. Quantification of the effect of energy imbalance on bodyweight. Lancet 2011;378:826–837; NHLBI. The Practical Guide: Identification, Evaluation, and Treatment of Overweight and Obesity in Adults (2000).

## Sources

- [Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (2005) — AMDR](https://nap.nationalacademies.org/catalog/10490)
- [FAO. Food energy — methods of analysis and conversion factors (Food and Nutrition Paper 77, 2003) — Atwater general factors](https://www.fao.org/4/y5022e/y5022e00.htm)
- Wishnofsky M. Caloric equivalents of gained or lost weight. Am J Clin Nutr 1958;6:542–546
- Hall KD et al. Quantification of the effect of energy imbalance on bodyweight. Lancet 2011;378:826–837
- [NHLBI. The Practical Guide: Identification, Evaluation, and Treatment of Overweight and Obesity in Adults (2000)](https://www.nhlbi.nih.gov/files/docs/guidelines/prctgd_c.pdf)

_Note: medical information, not professional advice._