Calorie Calculator: TDEE, Maintenance & Deficit

How the calculator works

Your daily calorie needs come from two numbers: what your body burns at rest, and how much you move on top of that. The calculator estimates the first with a published equation and the second with an activity multiplier.

Step 1: your resting burn (BMR) with Mifflin-St Jeor

Basal metabolic rate (BMR) is the energy your body uses to breathe, circulate blood and keep warm while you rest. The Mifflin-St Jeor equation, published in 1990, predicts it from weight, height, age and sex. It was built from measurements of healthy adults aged 19 to 78.

MenBMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5

WomenBMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) − 161

If you think in pounds and inches, the same equations read: 4.536 × weight (lb) + 15.875 × height (in) − 5 × age, then + 5 for men or − 161 for women.

A 2005 systematic review compared the common equations against measured resting energy use. Mifflin-St Jeor was the most reliable, landing within 10% of the measured value for more non-obese and obese adults than any other equation. A later study of 337 adults put it within 10% for 82% of people (87% of non-obese and 75% of obese adults), so treat your result as a starting point.

Step 2: activity multipliers

Your total daily energy expenditure (TDEE), also called maintenance calories, is your BMR times an activity factor. These multipliers are widely used conventions, so pick honestly and adjust later if your weight trend disagrees.

Activity level	What it looks like	Multiplier
Mostly sitting	Desk job, little planned exercise	1.2
Light	On your feet some of the day, or exercise 1 to 3 days a week	1.375
Moderate	Exercise 3 to 5 days a week	1.55
Very active	Hard exercise 6 to 7 days a week	1.725
Extra active	Physical job plus hard training	1.9

It's easy to overestimate how active you are. If you're unsure between two levels, choose the lower one.

Step 3: from maintenance to a daily target

To keep your weight, eat about your TDEE. To lose, eat below it. To gain, eat a little above it. The calculator offers small, steady changes and caps any deficit at 25% of your maintenance calories.

What a calorie deficit means

A calorie deficit means eating fewer calories than you burn, so your body makes up the gap from stored energy. A common rule of thumb says 3,500 kcal equals about 1 lb of body weight (about 7,700 kcal per kg). By that rule, eating 500 kcal a day below maintenance would mean losing about 1 lb a week.

Treat that rule as rough. Early weight changes include water and stored carbohydrate, and as you get lighter your maintenance calories fall, so the same deficit does less over time. In an analysis of 7 supervised diet studies with 103 adults, people lost an average of 20.1 lb where the 3,500 kcal rule predicted 27.6 lb. The NIH's free Body Weight Planner models this slowdown if you want a longer forecast.

The practical approach is simple. Start with a target, log your food, weigh yourself a few times a week and look at the 2 to 3 week trend. If the trend is flat and you want it to move, lower your target by 100 to 200 kcal. If it moves faster than planned, raise it.

Worked example in pounds

A 35-year-old woman is 5 ft 5 in (65 in, 165.1 cm) tall, weighs 170 lb (77.1 kg) and exercises 4 days a week.

BMR = 10 × 77.1 + 6.25 × 165.1 − 5 × 35 − 161 = 771 + 1,032 − 175 − 161 = about 1,467 kcal.
TDEE = 1,467 × 1.55 (moderate) = about 2,270 kcal. That's her maintenance.
To lose about 1 lb a week: 2,270 − 500 = about 1,770 kcal a day.

If she picked "lose about 1.5 lb a week", 2,270 − 750 would give 1,520 kcal. That cut is more than 25% of her maintenance, so the calculator shows about 1,710 kcal instead and explains why.

Worked example in kilograms

A 28-year-old man is 180 cm tall, weighs 85 kg and walks a lot at work but rarely trains.

BMR = 10 × 85 + 6.25 × 180 − 5 × 28 + 5 = 850 + 1,125 − 140 + 5 = 1,840 kcal.
TDEE = 1,840 × 1.375 (light) = 2,530 kcal.
To lose about 0.5 kg a week: 0.5 × 7,700 ÷ 7 = 550 kcal a day, so 2,530 − 550 = 1,980 kcal a day.

To gain slowly instead, he would eat about 2,530 + 250 = 2,780 kcal a day.

How low is too low?

As general guidance, calorie intake shouldn't fall below about 1,200 kcal a day for women or 1,500 kcal a day for men, except under the supervision of a health professional. For comparison, US obesity treatment guidelines prescribe 1,200 to 1,500 kcal a day for women and 1,500 to 1,800 kcal a day for men, or a deficit of 500 to 750 kcal a day, for weight loss. Going lower makes it hard to get enough protein, fiber, vitamins and minerals.

The calculator never shows a target under these floors. If your numbers land there, a smaller deficit with more activity is usually easier to keep up.

When to talk to a professional

Ask a doctor or registered dietitian for your target if any of these apply:

You're pregnant, trying to get pregnant or breastfeeding.
You have, or have had, an eating disorder, or counting calories makes you anxious.
You have diabetes, kidney, heart or thyroid disease, or another medical condition.
You take medicine that affects appetite, weight or blood sugar.
You're under 18.

Track your target in CaloriePix

A number only helps if you can see where your calories go. In CaloriePix you set a goal weight and weekly pace, and the app gives you a daily calorie and macro target plus an estimated goal date. Then you snap a photo of a meal, describe it or say it, check the AI estimate, and watch your day add up.

FAQ

How many calories should I eat to lose weight?

Start with your maintenance calories from the calculator and subtract about 250 to 500 kcal a day. For most people that means losing roughly 0.5 to 1 lb (0.25 to 0.5 kg) a week at first. Stay at or above about 1,200 kcal (women) or 1,500 kcal (men) unless a professional advises otherwise.

What's the difference between BMR and TDEE?

BMR is what your body burns at complete rest. TDEE adds everything else: daily movement, exercise and digesting food. Your TDEE is your maintenance calories.

How accurate is this calculator?

It's an estimate. Mifflin-St Jeor was the most reliable of the common equations in a systematic review, and in a later study it still missed by more than 10% for about 1 in 5 people. Your real maintenance shows up in your weight trend after 2 to 3 weeks of steady logging.

Should I eat back the calories I burn exercising?

Your activity level already includes your usual exercise. If you also add logged workouts on top, you count them twice. In CaloriePix, crediting exercise calories to your daily budget is a setting you can turn on or off, so pick one approach and stick with it.

Why has my weight loss slowed down?

As you lose weight, your body needs fewer calories, so the same intake creates a smaller deficit. Water shifts can also hide fat loss for a week or two. Re-run the calculator with your new weight every 5 to 10 lb (2 to 5 kg).

Is 1,200 calories a day safe?

For some smaller, less active women it's a reasonable floor. For many people it's too low to meet nutrient needs or keep up. If your calculated target is near 1,200 kcal, check it with a doctor or dietitian.

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. American Journal of Clinical Nutrition. 1990;51(2):241–247. doi:10.1093/ajcn/51.2.241
Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic Association. 2005;105(5):775–789. doi:10.1016/j.jada.2005.02.005
Hall KD, Sacks G, Chandramohan D, et al. Quantification of the effect of energy imbalance on bodyweight. The Lancet. 2011;378(9793):826–837. doi:10.1016/S0140-6736(11)60812-X
Frankenfield DC. Bias and accuracy of resting metabolic rate equations in non-obese and obese adults. Clinical Nutrition. 2013;32(6):976–982. doi:10.1016/j.clnu.2013.03.022
Thomas DM, Martin CK, Lettieri S, et al. Can a weight loss of one pound a week be achieved with a 3500-kcal deficit? Commentary on a commonly accepted rule. International Journal of Obesity. 2013;37(12):1611–1613. doi:10.1038/ijo.2013.51
National Institute of Diabetes and Digestive and Kidney Diseases (NIH). Body Weight Planner
U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020–2025, Appendix 2: Estimated Calorie Needs. (The 2025–2030 edition does not include a calorie needs table.)
Harvard Health Publishing. Calorie counting made easy. 2024.
Jensen MD, Ryan DH, Apovian CM, et al. 2013 AHA/ACC/TOS guideline for the management of overweight and obesity in adults. Circulation. 2014;129(25 Suppl 2):S102–S138. doi:10.1161/01.cir.0000437739.71477.ee

Track it in CaloriePix
Set this as your daily target in the app, then snap a photo of each meal to see your day add up.