Astras is a club — your personal AI wellness assistant. In the app, this target recalculates itself whenever your profile changes.
Calorie calculator
Calorie and macro calculator: daily calories, protein, fat and carbs
This free calculator estimates how many calories your body uses in a day (your TDEE) and turns that into a daily target for three goals — lose weight, maintain or build muscle — with protein, fat and carbs in grams. It uses the Mifflin-St Jeor equation and exactly the same math as the Astras app.
Calculate your daily calories and macros
years
Enter an age from 16 to 90.
Height
ft
in
cm
Enter a height from 4′7″ to 6′10″.
Weight optional
lb
kg
Enter a weight from 88 to 331 lb, or leave it empty.
Lose weight—
Maintain—your target
Build muscle—
- Protein
- —
- Fat
- —
- Carbs
- —
Resting (BMR)—
Gentle mode For your body, a lower target wouldn’t cover the minimum protein, fat and carbs, so Lose weight stays at your maintenance number.
Fill in sex, age and height — your numbers appear here.
Calculated in your browser. Nothing is sent or saved.
How to use the calorie calculator
Sex
Female, Male, or Prefer not to say (a neutral calculation halfway between the two).
Age
16 to 90. Astras is for ages 16 and up.
Height
4′7″ to 6′10″ (140–210 cm).
Weight (optional)
88 to 331 lb (40–150 kg). Leave it blank and the calculator uses a healthy reference weight for your height.
Daily activity
Passive (mostly sitting), Moderate (everyday activity with walks — the default) or Active (regular training or a physically active job).
Goal
Lose weight, Maintain or Build muscle.
You get three calorie targets — one per goal — and the protein, fat and carbs for the goal you picked. Nothing you enter leaves your browser.
What the numbers mean
- BMR — calories your body uses at rest, from the Mifflin-St Jeor equation.
- Maintenance (TDEE) — BMR × 1.2 (Passive), 1.375 (Moderate) or 1.55 (Active).
- Goal target — maintenance × 0.8, × 1 or × 1.15, rounded to 10 cal, never below a floor.
- Macros — protein in grams per kilogram of body weight, fat as a share of calories (at least 0.8 g/kg), carbs the rest (at least 130 g). At 4 cal per gram of protein and carbs and 9 per gram of fat, they add up to the target.
Example: a 32-year-old woman, 5′5″, 150 lb, moderately active
| Step | Calculation | Result |
|---|---|---|
| Healthy weight range for 5′5″ (165 cm) | BMI 18.5–24.9 | 111–149 lb (50.4–67.8 kg) |
| Weight used | 150 lb = 68 kg, just above the range: top of range + ¼ of the excess | 67.84 kg (149.6 lb) |
| BMR (Mifflin-St Jeor) | 10 × 67.84 + 6.25 × 165 − 5 × 32 − 161 | ≈ 1,389 cal |
| Maintenance (TDEE) | 1,388.7 × 1.375 = 1,909.4 | 1,910 cal |
| Lose weight | 1,909.4 × 0.8 = 1,527.5 | 1,530 cal |
| Build muscle | 1,909.4 × 1.15 = 2,195.8 | 2,200 cal |
| Goal | Calories | Protein | Fat | Carbs |
|---|---|---|---|---|
| Lose weight | 1,530 | 122 g (1.8 g/kg) | 54 g | 139 g |
| Maintain | 1,910 | 95 g (1.4 g/kg) | 54 g | 261 g |
| Build muscle | 2,200 | 136 g (2.0 g/kg) | 54 g | 293 g |
Fat is the same in all three rows: the share of calories (30%, 25%, 22%) would give 51, 53 and 54 g, so the minimum of 0.8 g per kg — 54 g — applies. Carbs are what’s left: for maintenance, (1,910 − 95 × 4 − 54 × 9) ÷ 4 = 261 g.
The same woman at Passive gets 1,450 / 1,670 / 1,920 cal; at Active, 1,720 / 2,150 / 2,480.
Calorie calculator for weight loss: how the deficit is set
“Lose weight” is 20% below your maintenance, with two floors. The first is fixed: 1,200 cal for women (and for “Prefer not to say”), 1,500 for men. The second depends on your body: the target must fit the protein for your goal, fat of 0.8 g/kg and 130 g of carbs.
The second floor matters often. For the woman above at Passive, −20% would be 1,333 cal — too little for 109 g protein, 54 g fat and 130 g carbs — so her target stays at 1,450, about 13% below maintenance. For some small, older bodies there’s no room for a deficit at all: a 70-year-old woman, 4′11″, 99 lb, Passive gets 1,200 cal for both Lose weight and Maintain, and the calculator says so.
The target is not a forecast: it doesn’t say how fast or how much you’ll lose.
Macro calculator for women: protein, fat and carbs by goal
Protein per kilogram of body weight (per pound in brackets):
| Goal | Passive | Moderate | Active |
|---|---|---|---|
| Lose weight | 1.6 g (0.73) | 1.8 g (0.82) | 2.0 g (0.91) |
| Maintain | 1.2 g (0.54) | 1.4 g (0.64) | 1.7 g (0.77) |
| Build muscle | 1.8 g (0.82) | 2.0 g (0.91) | 2.2 g (1.0) |
Fat as a share of the calorie target, never below 0.8 g/kg:
| Goal | Passive | Moderate | Active |
|---|---|---|---|
| Lose weight | 32% | 30% | 28% |
| Maintain | 28% | 25% | 23% |
| Build muscle | 24% | 22% | 20% |
Carbs take the rest. Protein is set per kilogram, not as a percentage: with percentages, a lower calorie target would mean less protein exactly when you want to keep muscle. The tables are the same for women and men.
How much protein per day for a woman?
In Astras, 1.2 to 2.2 g per kilogram of body weight a day — about 0.54 to 1.0 g per pound — depending on goal and activity. For the 5′5″, 150-lb woman above, that’s 81 to 149 g:
| Goal | Passive | Moderate | Active |
|---|---|---|---|
| Lose weight | 109 g | 122 g | 136 g |
| Maintain | 81 g | 95 g | 115 g |
| Build muscle | 122 g | 136 g | 149 g |
The commonly cited minimum for adults (RDA) is 0.8 g/kg; the Astras range starts above it, and the steps for active people follow the International Society of Sports Nutrition’s position on protein and exercise. Leave weight blank, and protein is counted from the reference weight: 59 kg (130 lb) for a 5′5″ woman, 83 g at Maintain and Moderate.
Why your weight counts only partly above the healthy range
Within the healthy range (BMI 18.5–24.9) your actual weight is used. Above it, the calculator takes the top of the range plus a quarter of the excess, so the target doesn’t grow with every extra pound; below it, the bottom of the range, so the target doesn’t lock in being underweight.
Example: a 45-year-old woman, 5′5″, 220 lb, Passive. Mifflin-St Jeor with the full 220 lb gives about 1,970 cal for maintenance; the calculator counts 167 lb and gives 1,680. Protein comes from the same 167 lb: 91 g at Maintain.
Ages 16–18 and 60+
Mifflin-St Jeor was built on adults. At 16–17 the calculator uses the Schofield equation (FAO/WHO/UNU), made for teenagers; at 18 the two are blended half and half; from 19 it’s Mifflin-St Jeor alone. Between 60 and 70 the healthy range shifts gradually to the higher range used for older adults (BMI 23–27 from 70).
In Astras, your target updates itself
The same formula sets your daily target in the app, free for everyone. Change your height, weight, age, sex or activity — or log a new weigh-in — and the target and macros recalculate; one number is used on the calorie card, the Nutrition tab, in Karina AI’s answers and in the widget. In the app’s calorie panel you can switch goal and activity level or set your own number with a slider, down to the same floors; “Where this target comes from” shows a height-by-age table and the sources.
Then log meals by photo, voice or text with the AI calorie counter and find dishes with calories and macros among Karina’s recipes. Plans start from $4.99/month — see pricing.
Sources
- Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241–247. PubMed 2305711
- Schofield WN. Predicting basal metabolic rate, new standards and review of previous work. Hum Nutr Clin Nutr. 1985;39 Suppl 1:5–41. PubMed 4044297
- Jäger R et al. ISSN Position Stand: protein and exercise. J Int Soc Sports Nutr. 2017;14:20. PMC5477153
Frequently asked questions
-
Roughly 1,600–2,400 cal a day for adult women and 2,000–3,000 for men, by the Dietary Guidelines for Americans — your own number depends on sex, age, height, weight and activity. Here, maintenance is your resting metabolic rate from Mifflin-St Jeor times 1.2, 1.375 or 1.55. A 32-year-old woman, 5′5″, 150 lb and moderately active comes out at about 1,910 cal a day to maintain; a 35-year-old man, 5′11″, 176 lb at the same level, about 2,410. Treat your result as a starting point and watch how your weight and energy respond over a few weeks.
-
In this calculator, “Lose weight” is 20% below your maintenance, but never below 1,200 cal for women or 1,500 for men, and never below what your minimum protein, fat and carbs need. For the 5′5″, 150-lb woman at Moderate activity, that’s 1,530 cal. If the floors push the target up, the deficit is smaller than 20%, and for some small bodies there’s no room for a deficit at all — the calculator shows maintenance instead. It doesn’t predict how fast you’ll lose weight, and it isn’t advice for pregnancy, medical conditions or eating disorders.
-
BMR (basal or resting metabolic rate) is the energy your body uses at rest — breathing, circulation, keeping warm. TDEE (total daily energy expenditure) adds everything you do during the day. This calculator estimates BMR with the Mifflin-St Jeor equation and multiplies it by an activity factor to get TDEE, shown as your “Maintain” target. For the 5′5″, 150-lb woman, BMR is about 1,389 cal and TDEE about 1,910 at Moderate activity. Both are estimates from an equation; a lab measurement of your own metabolism can differ.
-
Choose by your typical day, not your best one. Passive (1.2) fits mostly sitting days — desk work, little walking. Moderate (1.375) is everyday activity with walks and is the default. Active (1.55) is for regular training or a physically active job. There’s deliberately no “very active” level: people tend to overestimate their activity, and the top level is kept moderate. Steps and workouts from Apple Health or Health Connect aren’t added to the target — you pick the level yourself, in the calculator and in the app.
-
It’s a good starting estimate, not a measurement. Mifflin-St Jeor was derived from measured resting energy expenditure in healthy adults and is widely used for that reason, but any one person can differ from the prediction, and the activity level you choose adds its own error. Use the result as a starting target: keep it for a few weeks, watch the trend in your weight and how you feel, and adjust. People with medical conditions should get a target from their doctor or dietitian.
-
Usually for one of four reasons. Weight above the healthy range counts only partly here, while many calculators use your full weight. There are three activity levels, topping out at 1.55. Floors keep the target from dropping below 1,200 or 1,500 cal and below your minimum protein, fat and carbs. And protein is set in grams per kilogram (1.2–2.2), not as a percentage of calories. Results are rounded to 10 cal. For an adult with a weight inside the healthy range, maintenance matches plain Mifflin-St Jeor times the activity factor.
-
No — this page doesn’t give a number for pregnancy or breastfeeding, because energy needs change and depend on more than an equation. Ask your doctor or midwife. For reference, in the Astras app turning on pregnancy removes the “Lose weight” goal altogether, because a deficit isn’t appropriate, and adds calories by trimester: none in the first, 340 in the second and 450 in the third (300 if the date isn’t set), counted from the first day of your last period. Breastfeeding isn’t factored into the app’s calorie target.
-
No. The calculation runs in your browser; your age, height, weight and goal aren’t sent to Astras or saved, and you don’t need an account to use it. If you sign up, the app asks for the same details in your profile, keeps them in your account so the target is the same on every device, and recalculates when they change. In the app there are no ads, we don’t sell your data for money (if you allow ad measurement, California law counts it as “sharing” and a “sale”), and you can export your data or delete your account at any time.
In Astras, your target updates itself
Change your weight, activity or goal, and the app recalculates your target and macros — free for everyone.