How many calories should I eat a day to lose weight?

Create a deficit of 300–500 calories below your TDEE. A 500-calorie daily deficit creates roughly a 1-pound-per-week loss (since 3,500 calories ≈ 1 lb of fat). Deficits over 700/day tend to cause muscle loss and metabolic adaptation. Use our calculator to find your TDEE first, then subtract 300–500.

What is the difference between BMR and TDEE?

BMR (Basal Metabolic Rate) is the calories your body burns at complete rest — just to keep organs functioning. TDEE (Total Daily Energy Expenditure) adds your activity level to BMR. TDEE is the relevant number for planning your diet, since very few people are completely sedentary.

Do calorie needs change as you age?

Yes. BMR declines roughly 1–2% per decade after age 20, primarily due to loss of muscle mass. A 50-year-old has about 10–15% lower calorie needs than a 20-year-old at the same weight. Resistance training counteracts this by maintaining muscle.

How many calories do I need to gain muscle?

A modest calorie surplus of 200–300 cal/day above TDEE, combined with resistance training, supports lean muscle gain with minimal fat. Larger surpluses ("dirty bulking") add fat rapidly without proportionally more muscle.

Is 1,200 calories a day safe?

For most adults, 1,200 calories is too low. The minimum generally recommended by dietitians is 1,200 for women and 1,500 for men — and only under medical supervision. Below these thresholds, nutrient deficiency and muscle loss become significant risks. Our calculator will never recommend a target below these minimums.

How accurate is the Mifflin-St Jeor equation?

Mifflin-St Jeor is the most accurate formula for predicting RMR in both normal-weight and obese individuals, validated to within ±10% for most people in a 2005 Academy of Nutrition and Dietetics review. It outperforms the older Harris-Benedict equation. However, individual variation exists — use the output as a starting point and adjust based on 2–4 weeks of real-world results.

Calorie Calculator

Health & Fitness

Daily calorie needs based on your goals

Weight (kg)

Height (cm)

Age

Gender

Activity Level

Goal

Calories are the fundamental currency of body weight — eat more than you burn and you gain weight, eat less and you lose it. Yet most people have no idea how many calories their body actually needs each day. The standard "2,000 calorie diet" you see on nutrition labels is a rough average for a sedentary adult woman. It's wrong for most individuals, and wildly wrong for athletes, teenagers, pregnant women, or anyone with an active job.

Our free calorie calculator uses the most accurate formula available — the Mifflin-St Jeor equation, validated in a 2005 meta-analysis of 10 studies — to estimate your Total Daily Energy Expenditure (TDEE): the number of calories you burn in a typical day. Enter your age, sex, height, weight, and activity level, and the tool instantly shows you how many calories you need to maintain, lose, or gain weight.

Whether you're tracking macros, starting a fitness program, or simply curious about your nutrition, this calculator gives you a personalised baseline grounded in science.

Why Calorie Calculator Matters

Calorie knowledge transforms vague health goals into concrete, actionable plans. Without knowing your maintenance calories, "eating healthy" is guesswork. With it, you can create a precise calorie deficit for weight loss (typically 300–500 calories below maintenance), a surplus for muscle gain (200–300 calories above), or hit maintenance for weight stability.

According to the World Health Organization, overweight and obesity (driven primarily by chronic calorie surplus) affect more than 1 billion people worldwide. At the same time, under-eating and calorie restriction disorders affect hundreds of millions more. Both stem partly from the same problem: people don't know their actual calorie needs.

This calculator is used daily by fitness enthusiasts monitoring macros, healthcare professionals setting patient nutrition targets, and parents planning family meals.

The Calorie Calculator Formula, Explained

TDEE = BMR × Activity Multiplier

Step 1 — Calculate BMR using the Mifflin-St Jeor equation:

Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5

Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161

Step 2 — Multiply BMR by your activity level:

Sedentary (desk job, no exercise): BMR × 1.2

Light (light exercise 1–3 days/week): BMR × 1.375

Moderate (moderate exercise 3–5 days/week): BMR × 1.55

Active (hard exercise 6–7 days/week): BMR × 1.725

Very active (twice-daily training or physical job): BMR × 1.9

The result is your TDEE — the calories needed to maintain your current weight. For weight loss, subtract 300–500/day. For muscle gain, add 200–300/day.

How to Use the Calorie Calculator: Step by Step

Enter your stats
Input your age, sex, height (cm or ft/in), and current weight (kg or lbs).
Select activity level
Be honest — most people overestimate activity. If you sit at a desk all day and exercise 3×/week, choose "moderate" not "very active."
Read your TDEE
This is your maintenance calorie count. The calculator also shows calorie targets for weight loss (−500/day = −1 lb/week) and muscle gain.
Set your target
For weight loss, aim for 300–500 calorie deficit. For muscle gain, aim for 200–300 surplus. Extremes (>700 deficit or >500 surplus) are counterproductive for most people.
Track and adjust
Calorie needs shift as you lose or gain weight. Recalculate every 4–6 weeks and adjust your intake accordingly.

Calorie Calculator Examples: Real-World Scenarios

28-Year-Old Woman, Office Worker, Wants to Lose Weight

Lisa, 28, 5'5" (165cm), 155 lbs (70.5kg), desk job, walks 30 min most days.

Age:28

Sex:Female

Height:165cm

Weight:70.5kg

Activity:Light (1.375)

Calculation

BMR = (10×70.5) + (6.25×165) − (5×28) − 161 = 705+1031−140−161 = 1,435 | TDEE = 1,435×1.375 = 1,973 cal/day

Result

Maintenance: 1,973 cal/day. For 1 lb/week loss: 1,473 cal/day. At this deficit, Lisa reaches 140 lbs in ~15 weeks without extreme restriction.

35-Year-Old Male Athlete, Wants to Build Muscle

Marcus, 35, 5'11" (180cm), 178 lbs (80.8kg), lifts weights 5×/week.

Age:35

Sex:Male

Height:180cm

Weight:80.8kg

Activity:Active (1.725)

Calculation

BMR = (10×80.8)+(6.25×180)−(5×35)+5 = 808+1125−175+5 = 1,763 | TDEE = 1,763×1.725 = 3,041 cal/day

Result

Maintenance: 3,041. For lean muscle gain (+250 surplus): 3,291 cal/day. At this level, Marcus can expect 0.25–0.5 lbs lean muscle weekly.

50-Year-Old Post-Menopause, Weight Maintenance

Sandra, 50, 5'4" (162cm), 148 lbs (67.3kg), walks daily, yoga 2×/week.

Age:50

Sex:Female

Height:162cm

Weight:67.3kg

Activity:Light (1.375)

Calculation

BMR = (10×67.3)+(6.25×162)−(5×50)−161 = 673+1012−250−161 = 1,274 | TDEE = 1,274×1.375 = 1,752

Result

Maintenance: 1,752 cal/day — notably lower than at 28 due to metabolic slowdown. Sandra should not eat like she did in her 30s if weight management is a goal.

Common Mistakes to Avoid

Overestimating activity level — selecting "very active" when actually "moderate" inflates your calorie allowance by 200–400 cal/day, sabotaging weight loss.
Not accounting for calorie density — 500 calories of broccoli fills a large bowl; 500 calories of peanut butter is 2 tablespoons. Volume of food ≠ calorie content.
Eating back all exercise calories — fitness apps often overestimate calorie burn. Add only 50–75% of tracked workout calories to avoid overcorrection.
Setting too aggressive a deficit — below 1,200 cal/day for women or 1,500 for men causes muscle loss, fatigue, and metabolic adaptation that makes future weight loss harder.

Tips & Tricks

Protein intake of 0.7–1.0g per pound of body weight preserves muscle during a calorie deficit.
Muscle burns more calories at rest than fat — resistance training increases your TDEE over time, making weight management easier long-term.
Liquid calories are easy to miss. A daily Starbucks latte can add 200–350 hidden calories.

Knowing your daily calorie needs is the foundation of any nutrition plan, whether your goal is weight loss, muscle building, athletic performance, or simply staying healthy. Use our calorie calculator as your starting point, track your intake for a few weeks, and adjust based on actual results. For clinical nutrition guidance, the National Institutes of Health and the Academy of Nutrition and Dietetics provide evidence-based dietary reference intakes.

Calorie Calculator — Frequently Asked Questions

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Authoritative References

NIH — Dietary Guidelines for Americans

dietaryguidelines.gov — Official US daily calorie and nutrient guidance

WHO — Healthy Diet Fact Sheet

who.int — Global dietary recommendations

External links open in a new tab. OmniCalc.us is not affiliated with these organisations.

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