Calorie Deficit Calculator (TDEE + BMR) & Complete Guide

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title: "Calorie Deficit Calculator (TDEE + BMR) & Complete Guide" description: "Free calorie deficit calculator using Mifflin-St Jeor — get your BMR, TDEE, and recommended daily calories for losing or gaining weight." publishedAt: "2026-05-19" updatedAt: "2026-05-19" author: "Inlab Products" tags: ["calorie deficit calculator", "TDEE calculator", "BMR calculator", "how many calories to lose weight"] keyTakeaways:

• "Your BMR is the calories you burn at rest; TDEE adds activity. Daily calorie target = TDEE - deficit (loss) or TDEE + surplus (gain)."
• "A safe deficit is roughly 10–25% below TDEE. 0.5–1% of body weight lost per week is sustainable; faster than that means more muscle and water, not just fat."
• "For weight gain, 250–500 kcal above TDEE typically supports 0.25–0.5 kg/week gain with most of that being lean mass — if you train."
• "The Mifflin-St Jeor equation is the most validated BMR formula for adults. Katch-McArdle is more accurate if you know your body-fat percentage."
• "All formulas are estimates. Track your actual weight trend for 2–3 weeks, then adjust your target up or down by ~100–150 kcal/day." faq:
• question: "How many calories should I eat to lose weight?" answer: "Subtract 15–25% from your TDEE. For most adults that's a 300–700 kcal/day deficit. Start in the middle of that range, track your weight for 2–3 weeks, and adjust. Going lower than 25% deficit usually backfires — energy crashes, muscle loss, and binging — without speeding up fat loss meaningfully."
• question: "How accurate is the Mifflin-St Jeor BMR equation?" answer: "It's the most validated equation for healthy adults, typically within ±10% of measured BMR. It tends to overestimate slightly for very obese individuals and underestimate for very lean, muscular ones. If you know your body fat, the Katch-McArdle formula is more accurate."
• question: "What's a safe rate of weight loss?" answer: "0.5–1% of body weight per week is the sustainable range. For a 75 kg / 165 lb adult, that's about 0.4–0.75 kg (1–1.6 lb) per week. Faster than this and a meaningful portion of the loss is water and muscle, not fat — and you're more likely to rebound."
• question: "Why are the calculator's numbers different from my fitness tracker?" answer: "Most fitness watches overestimate calorie burn from exercise by 20–40%. Our calculator uses activity-multiplier brackets derived from research-validated TDEE studies, not watch estimates. If your watch and our calculator disagree, the calculator is usually closer to reality."
• question: "Do I need to eat at a deficit every single day?" answer: "No. Most research shows weekly average matters more than daily exactness. A higher-calorie day (a family dinner, a holiday) is fine if the rest of the week balances out. Obsessive daily exactness is what leads to abandonment."

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This calculator gives you a starting estimate for daily calorie targets. Plug in your numbers, get a target. The article below explains the math and how to adjust.

Free TDEE & calorie calculator

Mifflin-St Jeor formula. All math is on-device — nothing leaves your browser.

Sex (biological)

FemaleMale

Goal

LoseMaintainGain

Age (years)ActivitySedentary (desk job)Light (1–3 days/wk)Moderate (3–5 days/wk)Very active (6–7 days/wk)AthleteHeight (cm)Weight (kg)

BMR

1,370

kcal/day at rest

TDEE

2,124

to maintain weight

Lose weight

1,699

kcal/day target

Estimates assume a 20% deficit (lose) or 12% surplus (gain). For a different deficit, eat below TDEE by the % that fits your timeline. Re-check your target every 2–3 weeks based on actual weight trend.

What is BMR?

Basal Metabolic Rate (BMR) is the energy your body burns to keep you alive at rest — breathing, circulating blood, maintaining body temperature, building and repairing cells. For most adults, BMR accounts for 60–75% of total daily calorie burn.

The most validated formula for estimating BMR in healthy adults is the Mifflin-St Jeor equation:

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

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

For a 30-year-old woman, 165 cm, 65 kg: BMR ≈ (10×65) + (6.25×165) − (5×30) − 161 = 650 + 1031 − 150 − 161 = 1,370 kcal.

What is TDEE?

Total Daily Energy Expenditure (TDEE) is BMR plus the calories you burn from activity. It's the number you actually need to know for weight management.

The standard approach is to multiply BMR by an activity multiplier:

Most people overestimate their activity level. If you have a desk job and lift weights 3× a week, you're moderately active, not very active. Round down if you're unsure.

For our example (BMR 1,370, moderately active): TDEE ≈ 1,370 × 1.55 = 2,124 kcal/day.

Calorie deficit for weight loss

Eat below TDEE; lose weight. The classic estimate is that 3,500 kcal ≈ 1 lb (0.45 kg) of fat — so a 500 kcal/day deficit produces roughly 1 lb per week.

This is approximately right early on but becomes less accurate as you lose weight, because BMR drops slightly with body mass. The NIH Body Weight Planner accounts for this adaptation.

Recommended deficit ranges:

Calorie surplus for weight gain

Eating above TDEE supports weight gain. For most adults, a 250–500 kcal/day surplus produces 0.25–0.5 kg/week gain. If you're training for muscle gain, this range maximizes lean-mass gain and minimizes fat gain.

For weight gain, what you eat matters more than for weight loss. A 400 kcal/day surplus of donuts produces more fat than the same surplus from protein-rich whole foods. See our healthy weight gain guide for specifics.

Adjust based on actual results

The calculator gives a starting point. The truth comes from your bathroom scale.

After 2–3 weeks on a target, check your weight trend:

• If you're losing 0.5–1% body weight/week, your target is right.
• If you're losing less than 0.3% body weight/week, drop your target by 100–150 kcal.
• If you're losing more than 1.5% body weight/week, raise your target by 100–150 kcal. (Faster isn't better.)
• If you're gaining and want to be losing (or vice versa), recalculate — your activity level may have shifted.

Don't adjust based on a single day's reading. Daily weight fluctuates ±1 kg from water, food in transit, sodium, and hormones. Look at the weekly average.

Why fitness-watch calories are usually wrong

Most popular fitness watches overestimate calorie burn from exercise by 20–40%, according to multiple validation studies (Shcherbina et al., 2017). Eating back "exercise calories" reported by a watch is a common reason people don't see the deficit they expect.

The activity multipliers in this calculator are derived from doubly labeled water studies — the gold-standard method for measuring TDEE — and tend to be more accurate than wearable-derived estimates.

How Callie uses these numbers

When you set a goal in Callie, the AI calculates your TDEE using the same Mifflin-St Jeor approach and applies a deficit or surplus matched to your timeline. As you log meals and your weight trend updates, the target self-adjusts — so you don't have to recompute by hand. See our guide to weight loss with a calorie tracker for the full workflow.

Sources

1. Mifflin MD, et al. (1990). "A new predictive equation for resting energy expenditure in healthy individuals." Am J Clin Nutr 51:241-247.
2. Frankenfield D, et al. (2005). "Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults." J Am Diet Assoc 105(5):775-789.
3. Shcherbina A, et al. (2017). "Accuracy in Wrist-Worn, Sensor-Based Measurements of Heart Rate and Energy Expenditure in a Diverse Cohort." J Pers Med 7(2):3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5524096/
4. NIH Body Weight Planner. https://www.niddk.nih.gov/bwp
5. Hall KD, et al. (2011). "Quantification of the effect of energy imbalance on bodyweight." Lancet 378(9793):826-837.
6. Trexler ET, et al. (2014). "Metabolic adaptation to weight loss: implications for the athlete." J Int Soc Sports Nutr 11:7.

Important: This calculator and guide are educational, not medical advice. If you have diabetes, are pregnant, have a history of disordered eating, or take medications that affect metabolism, consult a registered dietitian or physician before setting a calorie target.