Your body burns energy around the clock, even while you sleep. Two numbers describe that burn: BMR (Basal Metabolic Rate) is the calories you need just to stay alive at rest, and TDEE (Total Daily Energy Expenditure) is your BMR scaled up by how much you actually move. This calculator converts BMR to TDEE in one step, using the Mifflin-St Jeor equation that nutrition professionals rely on, so you land on a realistic maintenance-calorie number instead of a guessed one.
Adjust any input and the result updates instantly. The card shows your resting BMR, your activity-scaled TDEE in both kcal and kJ, your weekly burn, and the classic 500-kcal deficit/surplus targets for gradual weight loss or lean gains.
How to Use
- Choose your Sex. The Mifflin-St Jeor equation adds a small constant for men (+5) and subtracts a larger one for women (−161); picking the right one keeps the resting estimate honest.
- Enter your Age in completed years. Metabolism drifts downward as you age, so a 45-year-old and a 25-year-old with identical height and weight do not burn the same number of calories.
- Type your Height in centimeters. If you measure in inches, multiply by 2.54 first.
- Enter your Weight in kilograms. If you measure in pounds, multiply by 0.4536.
- Pick your Activity Level honestly. Most people underestimate this — a desk job with three gym visits per week is "moderate," not "very." Choosing a factor that is too high inflates your TDEE and hides why the scale is not moving.
The result card first reports BMR (kcal/day), the energy your organs and brain consume at complete rest. It then multiplies that by the activity factor to produce TDEE, the calories you would need to eat to hold your current weight. The "Weight-Loss Target" subtracts 500 kcal (a roughly 3,500-kcal weekly deficit, historically tied to about one pound of fat per week), and the "Weight-Gain Target" adds the same amount for a slow lean bulk.
The Two Equations Behind the Number
This calculator uses the Mifflin-St Jeor equation, published in 1990 and still the equation most recommended by dietitians because it matches measured resting metabolism more closely than older formulas like Harris-Benedict or the Revised Harris-Benedict:
- Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) + 5
- Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) − 161
From BMR you reach TDEE by multiplying by an activity factor:
- Sedentary (desk work, little exercise) → 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 hard training plus a physical job) → 1.9
Worked example: a 30-year-old man who is 175 cm tall and 70 kg, with a moderate activity level. His BMR is 10×70 + 6.25×175 − 5×30 + 5 = 700 + 1,093.75 − 150 + 5 = 1,648.75 kcal/day. Multiplying by 1.55 gives a TDEE of 2,555.56 kcal/day — that is roughly how much he must eat to hold his weight. Notice that exercise and daily movement add about 907 kcal on top of rest, which is why "BMR alone" badly understates what an active person actually needs.
Why the Activity Factor Is the Whole Game
Two people with the same BMR can have a TDEE that differs by more than 50 percent depending on how they classify themselves. A sedentary 1,649-kcal BMR becomes 1,979 kcal at factor 1.2, but 3,133 kcal at factor 1.9. That gap is over 1,100 kcal per day — more than a full extra meal.
Be conservative. If you train four days a week but sit at a desk the other eight hours, "moderate" (1.55) is the honest pick, not "very." After two weeks, weigh yourself under consistent conditions. If the scale does not move, your chosen factor was either too optimistic or too pessimistic, and you adjust the calories rather than trusting the equation blindly. The calculator is a starting estimate, not a verdict.
Examples
Example 1 — A moderately active man. A 30-year-old man, 175 cm, 70 kg, moderate activity. BMR = 1,648.75 kcal; TDEE = 2,555.56 kcal; weekly burn ≈ 17,888.94 kcal. A 500-kcal deficit puts him at 2,055.56 kcal/day for slow fat loss, while a 500-kcal surplus reaches 3,055.56 kcal/day for a gentle bulk.
Example 2 — A sedentary woman. A 25-year-old woman, 160 cm, 60 kg, sedentary. Her BMR is 10×60 + 6.25×160 − 5×25 − 161 = 600 + 1,000 − 125 − 161 = 1,314 kcal/day. At the 1.2 sedentary factor her TDEE is 1,576.80 kcal/day. Aiming for about a 20% deficit lands her near 1,260 kcal/day, a realistic cut that still leaves room for protein and vegetables.
Example 3 — A very active woman. A 40-year-old woman, 165 cm, 80 kg, very active (hard exercise most days). Her BMR is 1,470.25 kcal, and at factor 1.725 her TDEE is 2,536.18 kcal/day — far above what a "1,500 kcal diet" would allow, which is why generic calorie apps can leave active women underfed.
FAQ
What is the difference between BMR and TDEE?
BMR (Basal Metabolic Rate) is the energy you burn at complete rest — breathing, circulating blood, keeping your brain warm. TDEE (Total Daily Energy Expenditure) is BMR multiplied by an activity factor, so it includes walking, exercise, chores, and the thermic effect of digesting food. In short, BMR is your engine idling; TDEE is your engine driving through a normal day.
Which equation does this calculator use?
It uses the Mifflin-St Jeor equation, developed in 1990 and favored by registered dietitians because it predicts measured resting energy more accurately than the older Harris-Benedict formulas. It asks only for age, sex, height, and weight, then scales the result by your chosen activity level.
How do I choose my activity level?
Be realistic. Sedentary means a desk job with almost no intentional exercise (factor 1.2). Lightly active is light exercise 1–3 days a week (1.375). Moderately active is moderate exercise 3–5 days a week (1.55). Very active is hard exercise 6–7 days a week (1.725). Extra active is very hard training plus a physically demanding job (1.9). If you are unsure, pick the lower factor and verify against your two-week weigh-in trend.
How accurate is BMR-to-TDEE conversion?
Mifflin-St Jeor is usually within about 10 percent of measured resting metabolic rate, and the activity factor adds further uncertainty. Treat the result as a starting estimate, then calibrate: eat your estimated TDEE for two weeks and watch your weight. If the scale is flat, the factor was right; if it drops, you were eating below maintenance.
What calorie target should I use to lose weight?
A common evidence-informed starting point is a 500-kcal daily deficit from your TDEE, which historically supports roughly one pound (about 0.45 kg) of weight loss per week. The calculator shows this as the "Weight-Loss Target." Avoid dropping below about 1,200 kcal/day for women or 1,500 kcal/day for men without supervision, because overly aggressive deficits cost muscle and energy.
Should I eat at TDEE to maintain my weight?
Yes — your calculated TDEE is the maintenance figure. If your weight stays steady over two to three weeks at that intake, the activity factor you chose is correct. If you slowly gain, you were overestimating movement; if you slowly lose, you were underestimating it. Re-run the calculator with a different activity level until the scale agrees.
Disclaimer
This BMR to TDEE calculator is provided for informational purposes only and is not medical advice. Estimates are based on the Mifflin-St Jeor equation and the activity factors you select; they are approximations and do not account for body composition, genetics, thyroid conditions, medications, pregnancy, or clinical eating disorders. Individual energy needs vary significantly. Consult a registered dietitian or qualified healthcare provider before making major changes to your diet, especially if you have a medical condition, are pregnant or breastfeeding, or are treating a chronic disease.