Calorie & Macro Calculator [Free] — Deficit + Macros in 30 Sec

Your Details

Gender

Male

Female

Age

years

Height

Weight

Activity Level

💻

Sedentary

Little or no exercise, desk job

×1.2

🚶

Lightly Active

Light exercise 1-3 days/week

×1.375

🏃

Moderately Active

Moderate exercise 3-5 days/week

×1.55

🏋

Very Active

Hard exercise 6-7 days/week

×1.725

⚡

Extra Active

Very intense exercise, physical job

×1.9

Your Goal

Lose Weight

Maintain

Gain Weight

Target weight

0kcal

calories per day

Your BMI 0

Underweight Normal Overweight Obese

BMR: 0 · Formula used: Mifflin-St Jeor (1990)

BMR is the minimum calories your body burns at rest — just breathing, circulation, and keeping organs running.

⚕️ This calculator provides estimates for informational purposes only. Results are based on the Mifflin-St Jeor equation and may not account for individual medical conditions. Consult a healthcare professional before making significant dietary changes.

Track Automatically with CalZen AI

Just snap a photo of your food — CalZen recognizes it instantly and tracks your calories, macros, water, and more.

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How It Works

How the Calorie Calculator for Weight Loss Works

This calculator uses the Mifflin-St Jeor equation (1990) to estimate your Basal Metabolic Rate (BMR) — the number of calories your body needs at complete rest. It then multiplies your BMR by an activity factor to determine your Total Daily Energy Expenditure (TDEE).

The Mifflin-St Jeor equation was found to be the most accurate predictive equation for healthy individuals in a systematic review of 18 studies by Frankenfield et al., published in the Journal of the American Dietetic Association (2005). It predicts resting metabolic rate within 10% of measured values in more subjects than any other equation.

Formula	Equation	Accuracy
Mifflin-St Jeor (default)	10×W + 6.25×H - 5×A ± s	Most accurate (ADA)
Harris-Benedict (revised)	13.4×W + 4.8×H - 5.7×A + 88.4 (M)	Tends to overestimate
Katch-McArdle	370 + 21.6×LBM	Best for athletes (needs body fat %)

Body Mass Index

BMI Calculator — Body Mass Index

Body Mass Index (BMI) is a measure that assesses whether your weight is proportional to your height. It's calculated as weight (kg) / height (m)². BMI is used by the WHO and doctors worldwide as a primary screening tool for weight-related health risks.

Category	BMI	What it means
Underweight	< 18.5	Possible nutrient deficiency, weakened immune system. Medical consultation recommended.
Normal	18.5–24.9	Optimal range. Lowest weight-related health risks.
Overweight	25–29.9	Increased risk of cardiovascular disease and type 2 diabetes. A moderate calorie deficit can help.
Obese	≥ 30	Significantly elevated risk. A doctor-supervised weight loss plan is recommended.

BMI doesn't account for muscle mass, age, or fat distribution. Athletes with developed musculature may have an elevated BMI. For a more accurate assessment, use body fat percentage.

Guidelines

How Many Calories for Weight Loss?

The USDA Dietary Guidelines for Americans (2020-2025) provide estimated calorie needs by age, sex, and activity level:

Age	Women (sed./mod./active)	Men (sed./mod./active)
19-25	2,000 / 2,200 / 2,400	2,400-2,600 / 2,800 / 3,000
26-30	1,800 / 2,000 / 2,400	2,400 / 2,600 / 3,000
31-50	1,800 / 2,000 / 2,200	2,200 / 2,400 / 2,800
51-60	1,600 / 1,800 / 2,200	2,200 / 2,400 / 2,600
61+	1,600 / 1,800 / 2,000	2,000 / 2,200 / 2,600

For safe weight loss, the CDC recommends losing 1-2 pounds (0.5-1 kg) per week through a calorie deficit of 500-1,000 kcal/day. Minimum safe intake: 1,200 kcal/day for women, 1,500 kcal/day for men (NHLBI).

The Science

Why Tracking Calories Works

Research consistently shows that people who track what they eat are significantly more successful at losing weight:

Study	Finding	Source
Kaiser Permanente (2008)	People who kept daily food records lost 2× more weight	Am J Prev Med
Harvey et al. (2019)	Only 15 min/day of food logging needed for results	Obesity
Berry et al. (2021)	Digital self-monitoring = -2.87 kg significant weight loss	Obesity Reviews
Huntriss et al. (2024)	50% of active users achieved 5%+ weight loss	Obesity Sci & Pract
AI-Assisted Tracking (2024)	64% maintain changes vs 23% manual tracking	JMIR

"Those who kept daily food records lost twice as much weight as those who kept no records."
— Jack Hollis, Ph.D., Kaiser Permanente

FAQ

Frequently Asked Questions

How many calories should I eat per day?

It depends on your age, sex, height, weight, and activity level. Most adults need between 1,600-3,000 calories per day. Use the calculator above for a personalized estimate based on the Mifflin-St Jeor equation.

Which formula is the most accurate?

The Mifflin-St Jeor equation (1990) is considered the most accurate by the Academy of Nutrition and Dietetics. A 2005 systematic review by Frankenfield et al. found it predicts resting metabolic rate within 10% of measured values in more subjects than any other formula.

What is BMR vs TDEE?

BMR (Basal Metabolic Rate) is the calories your body burns at complete rest — just to keep you alive. TDEE (Total Daily Energy Expenditure) is your BMR multiplied by your activity level. TDEE is the number you should use to plan your diet.

How many calories for weight loss?

The CDC recommends a deficit of 500-1,000 calories per day for safe weight loss of 0.5-1 kg (1-2 lbs) per week. Never go below 1,200 kcal/day (women) or 1,500 kcal/day (men) without medical supervision.

How accurate are calorie calculators?

The Mifflin-St Jeor equation predicts BMR within ±10% for most healthy adults. However, individual variation exists. Use the calculator as a starting point and adjust based on your actual results over 2-3 weeks.

Should I count calories or macros?

Both matter. Total calories determine whether you gain, lose, or maintain weight. Macros (protein, carbs, fat) determine your body composition, energy, and health. For best results, track both — an app like CalZen makes this easy with AI food recognition.

What is the minimum safe calorie intake?

According to NHLBI guidelines: 1,200 kcal/day for women and 1,500 kcal/day for men. Very low calorie diets (below 800 kcal/day) should only be followed under medical supervision.

Does calorie tracking actually work?

Yes. A landmark Kaiser Permanente study (2008) found that people who kept daily food records lost twice as much weight. A 2024 study in JMIR showed that AI-assisted tracking helps 64% of users maintain dietary changes long-term, vs only 23% with manual methods.

References

Scientific Sources

1. Mifflin MD, St Jeor ST, et al. Am J Clin Nutr. 1990;51(2):241-7. PubMed →

2. Roza AM, Shizgal HM. Am J Clin Nutr. 1984;40(1):168-182. PubMed →

3. Frankenfield D, et al. J Am Diet Assoc. 2005;105(5):775-789. PubMed →

4. USDA. Dietary Guidelines for Americans 2020-2025. dietaryguidelines.gov →

5. Harvey J, et al. Obesity. 2019;27(3):380-384. PubMed →

6. CDC. Losing Weight. cdc.gov →

7. NHS. Understanding Calories. nhs.uk →

Last updated: March 2026

Calorie Calculator