Health Tools

Daily Calorie Calculator

Estimate your TDEE and calorie target for weight loss, maintenance, or gain. Based on the Mifflin-St Jeor equation.

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Calorie Calculator

Daily caloric needs based on your stats & goal

Age (years)

Sex

Height (cm)

Weight (kg)

Activity Level

Goal

About Calories

What is BMR vs TDEE?

BMR (Basal Metabolic Rate) is the calories your body burns at complete rest — just to keep your organs functioning. TDEE (Total Daily Energy Expenditure) multiplies BMR by your activity level to estimate total calories burned daily. Your TDEE is your maintenance calorie level.

What is a safe rate of weight loss?

Most health professionals recommend losing no more than 1–2 lbs (0.5–1 kg) per week. A 500 calorie/day deficit produces roughly 1 lb/week of fat loss. Larger deficits can cause muscle loss and metabolic adaptation.

How accurate are calorie calculators?

The Mifflin-St Jeor equation used here is the most validated formula for estimating resting metabolic rate, accurate within ±10% for most adults. Treat the result as a starting point and track your actual weight change for 2–3 weeks before adjusting — most people underestimate their true activity level.

Health Guide

Calorie Calculator Guide: BMR, TDEE & the Math of Weight Goals

A practical guide to calorie math — the Mifflin-St Jeor BMR formula, activity multipliers for TDEE, safe deficit and surplus ranges, and why "3,500 calories per pound" is an oversimplification you should still use anyway.

Written by Calculixy Editorial TeamReviewed by a registered dietitian (RDN)Updated: May 2026

From the Underwriting Desk

Calorie math is simpler than the diet industry suggests but more variable than the calculator output implies. The formula on the page gives you a number; your actual maintenance calories may be 10–15% above or below that estimate. That's not a flaw in the math — it's the reality that no equation can perfectly predict metabolic rate in any individual. The calorie calculator's job is to give you a defensible starting point. Your scale and energy levels over the following 2–4 weeks tell you whether the starting point was accurate.

What this calculator does

The Calorie Calculator estimates two numbers: your Basal Metabolic Rate (BMR) — the calories your body needs at complete rest to maintain basic functions — and your Total Daily Energy Expenditure (TDEE), which is BMR plus the calories you burn through activity. It uses the Mifflin-St Jeor equation, the most accurate widely-used BMR formula validated against indirect calorimetry, then applies an activity multiplier to arrive at TDEE.

From TDEE, the calculator estimates how many calories per day support weight loss, maintenance, or weight gain. The standard guidance: a 500-calorie daily deficit produces approximately 1 pound of weight loss per week; a 500-calorie surplus produces about 1 pound of gain per week.

When to use this calculator

To set a starting daily calorie target for a weight loss, gain, or maintenance goal
To estimate baseline metabolic rate for context (athletic recovery, illness, aging)
To compare your TDEE estimate against your tracked calorie intake when current weight is stable
To recalculate as your body changes — TDEE drops as you lose weight, rises as you gain muscle
To check whether a fitness app's calorie target is wildly off from a defensible baseline
To plan reasonable caloric ranges for athletes, hypothermic environments, or specific medical situations

The Mifflin-St Jeor formula

Developed in 1990 and validated in a 2005 meta-analysis as more accurate than the older Harris-Benedict equation, Mifflin-St Jeor is now the standard recommendation from the Academy of Nutrition and Dietetics.

Men

BMR = (10 × W) + (6.25 × H) − (5 × A) + 5

Women

BMR = (10 × W) + (6.25 × H) − (5 × A) − 161

Variable definitions

BMR = Basal Metabolic Rate (calories per day at complete rest)
W = Weight in kilograms
H = Height in centimeters
A = Age in years

The difference between the male and female versions reflects average differences in lean body mass at the same body weight. For individuals whose body composition differs significantly from the average (high muscle mass, very low body fat, etc.), the Katch-McArdle formula based on lean mass is more accurate — but requires a body fat percentage measurement most people don't have.

From BMR to TDEE — the activity multipliers

BMR represents calories burned at rest. TDEE adds the calories burned through movement, exercise, and the thermic effect of food. The most common approach uses activity multipliers:

TDEE = BMR × Activity Multiplier

Sedentary (1.2): Office work, minimal walking, no formal exercise. Most adults are here.
Lightly active (1.375): Light exercise or sports 1–3 days per week.
Moderately active (1.55): Moderate exercise 3–5 days per week, or physically active job.
Very active (1.725): Hard exercise 6–7 days per week, or physically demanding job + regular workouts.
Extra active (1.9): Twice-daily training, physical labor + intense exercise, professional athletes in season.

Most people overestimate their activity multiplier. A 30-minute walk plus a 45-minute gym session three times a week is "lightly active" (1.375), not "very active." Honest classification produces more accurate TDEE estimates.

Step-by-step example

A 35-year-old man, 178 cm tall, weighing 80 kg, who exercises 3 days per week.

BMR calculation (Mifflin-St Jeor, men):

BMR = (10 × 80) + (6.25 × 178) − (5 × 35) + 5 BMR = 800 + 1,112.5 − 175 + 5 BMR ≈ 1,742 calories/day

TDEE calculation (lightly active, 1.375):

TDEE = 1,742 × 1.375 ≈ 2,395 calories/day

Calorie targets:

Maintain weight: ~2,395 calories/day
Lose 1 lb/week: ~1,895 calories/day (500 deficit)
Lose 0.5 lb/week: ~2,145 calories/day (250 deficit)
Gain 0.5 lb/week: ~2,645 calories/day (250 surplus)

These are starting estimates. Over 2–4 weeks of consistent eating at the maintenance number, body weight stability confirms or refutes the estimate. Adjust by 100–200 calories per day in either direction if reality doesn't match prediction.

The "3,500 calories = 1 pound" rule and its limitations

This rule is the basis of most calorie-deficit math. It's a useful approximation derived from the energy density of body fat (roughly 3,500 kcal per pound), but it has known limitations:

Why it works in the short term

For the first 6–8 weeks of a moderate deficit, weight loss tracks reasonably close to the prediction. A 500-calorie daily deficit produces approximately 1 pound of fat loss per week, with some week-to-week variation from water weight and digestive contents.

Why it breaks down over time

As body weight drops, BMR drops with it — a smaller body burns fewer calories at rest. Activity-induced calorie burn drops at lower body weight as well. The Body Weight Planner from the NIH and academic research (notably from Kevin Hall at NIH) showed that real-world long-term weight loss is closer to half what the simple math predicts, because metabolism adapts.

What this means for goals

For 4–8 week goals, the simple 500/250 calorie deficit math is fine. For longer goals, recalculate TDEE every 10–15 pounds of body weight change and adjust accordingly. Plateaus aren't failures — they're often signs that TDEE has adapted and the deficit needs to be re-established.

Setting safe and sustainable deficits or surpluses

For weight loss

Conservative (250 kcal deficit, ~0.5 lb/week): Slow, very sustainable, minimal hunger or fatigue.
Moderate (500 kcal deficit, ~1 lb/week): The standard recommendation. Sustainable for most people for 2–4 months.
Aggressive (750–1,000 kcal deficit, ~1.5–2 lb/week): Faster results but increased hunger, fatigue, and muscle loss risk. Generally not recommended for more than 2–3 months at a time.
Extreme (>1,000 kcal deficit): Reserved for medically supervised programs. Sustained extreme deficits drive significant lean mass loss and metabolic adaptation.

For weight gain (muscle building)

Conservative (250 kcal surplus, ~0.5 lb/week): Slow, lean gains for trained lifters who already have meaningful muscle mass.
Moderate (500 kcal surplus, ~1 lb/week): Reasonable for beginners or returning lifters. Some fat gain is expected.
Aggressive (750+ kcal surplus): "Bulking" with significant fat gain. Used by some lifters but requires a planned cut phase afterward.

Minimum calorie floors: Most authorities recommend never dropping below 1,200 calories per day for women or 1,500 for men without medical supervision. Below these floors, nutrient adequacy becomes very difficult and metabolic adaptation accelerates.

Real-world use cases

1. Starting a weight loss plan

Calculate your TDEE honestly. Subtract 500 calories. Eat at that level for 2 weeks while tracking accurately. If weight drops by roughly 2 pounds, the estimate was accurate. If it stays flat, your real TDEE was 250–500 lower than the estimate — adjust down. If it drops faster, you overestimated activity — adjust up to a more sustainable rate.

2. Bodybuilding or muscle building

The cleanest progress comes from a small surplus (10–20% above TDEE) with consistent strength training. Track strength gains and body composition every 4 weeks. If strength is increasing and waist measurement isn't, the surplus is well-calibrated. If waist is growing fast while gym performance stays flat, the surplus is too large.

3. Athletic performance maintenance

Athletes in heavy training often need 3,000–5,000+ calories per day. Underfueling tanks performance, recovery, and immune function. Use the highest activity multiplier (1.9) for athletes in season; recalculate when training volume drops in off-season.

4. Maintaining weight after loss

The most common failure point in dieting isn't the loss phase — it's the return to maintenance. After significant weight loss, recalculate TDEE at your new weight. Add calories gradually back to that level. Track for 4–6 weeks at maintenance before assuming you're stable.

5. Adjusting with age

BMR drops gradually with age — roughly 1–2% per decade after 25–30. The same calorie intake that maintained weight at 25 will cause slow gain at 45 without adjustment. Recalculate every few years.

Common mistakes

Overestimating activity level. The single biggest source of error in calorie estimates. Most office workers who exercise 3–4 days/week are "lightly active," not "moderately active." This single overestimate can add 200–300 calories to a daily target.
Trusting calorie counts on food labels at 100%. Food label calorie counts are allowed up to 20% variance by FDA rules. Real-world tracking is rarely more precise than ±5%.
Forgetting liquid calories. Drinks (alcohol, sweetened coffee, juice, soda) often go uncounted. A daily 16-oz beer adds about 200 calories — enough to neutralize a moderate deficit completely.
Eating "back" exercise calories. Fitness trackers commonly overestimate exercise calorie burn by 20–40%. Eating back 100% of estimated burn often eliminates a planned deficit.
Restricting too aggressively. Extreme deficits cause hunger that derails consistency, muscle loss that lowers metabolism, and rebound eating that erases progress. Moderate, sustainable deficits beat aggressive ones over months.
Skipping weighing portions. Eyeballing portion sizes routinely results in 30%+ underestimates. A food scale is the cheapest accuracy upgrade in calorie tracking.
Treating the number as static. TDEE changes as weight changes. Recalculate every 10–15 lbs of weight change.
Ignoring sleep and stress. Sleep deprivation and chronic stress affect hunger hormones (leptin, ghrelin) and make any calorie target harder to hit consistently.

Frequently asked questions

How many calories should I eat per day?

Your TDEE is your maintenance number. Subtract 250–500 for weight loss; add 250–500 for weight gain. Your TDEE depends on age, sex, weight, height, and activity level — there's no single right answer for everyone.

What's the difference between BMR and TDEE?

BMR is your calorie burn at complete rest — what your body needs to maintain basic functions like breathing, circulation, and cell maintenance. TDEE is BMR plus the calories burned through movement, exercise, and the thermic effect of food. TDEE is always higher than BMR.

Is the Mifflin-St Jeor formula accurate?

It's the most accurate widely-used BMR estimate, with individual error typically within ±10%. The Katch-McArdle formula is more accurate but requires a measured body fat percentage. For most people without lab-measured body composition, Mifflin-St Jeor is the right choice.

How much weight can I safely lose per week?

Most clinical guidelines recommend 0.5–2 pounds per week. The high end is reasonable for shorter-term, higher-starting-weight situations. For longer-term and lower-starting-weight loss, 0.5–1 pound per week is more sustainable. Faster loss increases muscle loss risk and is harder to maintain.

Do I need to count calories forever?

Not necessarily. After 3–6 months of consistent tracking, most people develop strong intuition about portion sizes and meal compositions that match their goals. Many maintain successfully without ongoing tracking after that. Restarting tracking during goal phases or after weight regain is common and useful.

What about macronutrients?

Total calories drive weight change; macronutrients drive body composition and how you feel. For weight loss with muscle preservation, the standard guidance is 0.7–1.0 grams of protein per pound of body weight, fats at 20–30% of calories, carbohydrates filling the remaining calorie allotment.

Why does my calorie target keep changing?

TDEE drops as you lose weight (smaller body burns less). Activity may decrease as energy drops. Metabolic adaptation can reduce TDEE 5–15% below the formula prediction during sustained deficits. All of these mean target calories should be recalculated periodically during a long fat loss phase.

Are calorie calculators accurate?

They're accurate as starting estimates within about ±10%. The math is solid; the individual variation in BMR isn't captured by any formula. Use the calculator to set a target, then adjust based on actual results over 2–4 weeks.

Related Calculixy calculators

From the editorial desk: A calorie calculator is a hypothesis, not a fact. The formula gives you a number that's defensible as a starting point. Your scale, your energy, and your sleep over the following weeks confirm or refute that hypothesis. Patient people get this right by adjusting in small increments. Impatient people swing wildly and never settle. The math doesn't change — only the discipline to work with imperfect estimates does.

Calculixy's Calorie Calculator provides estimates for educational use only and does not constitute medical or nutritional advice. Calorie needs vary by individual based on metabolism, medical conditions, medications, and many factors no formula can fully capture. Consult a registered dietitian or healthcare provider before making significant dietary changes, especially if you have medical conditions, are pregnant, are recovering from an eating disorder, or are working with athletes or growing youth. All calculations run locally in your browser; Calculixy does not collect or transmit the values you enter.