Mifflin-St Jeor BMR and TDEE: How Daily Calorie Estimates Work

BMR vs TDEE in one minute

Basal Metabolic Rate (BMR) estimates the calories your body uses at complete rest to keep vital systems running. Total Daily Energy Expenditure (TDEE) multiplies that baseline by an activity factor so the number reflects a normal day with movement, work, and exercise.

People search for “maintenance calories” when they want TDEE. People search for “BMR calculator” when they want the resting baseline. ShishwaLab’s BMR tool shows both, then adjusts for a mild deficit or surplus if you pick a goal.

Why Mifflin-St Jeor

Several equations exist (Harris–Benedict, Katch–McArdle, and others). Mifflin-St Jeor is widely used for healthy adults because it tends to track measured resting energy expenditure reasonably well in general populations. It uses sex, age, height, and weight—no body-fat percentage required.

Male form: BMR = (10 × kg) + (6.25 × cm) − (5 × age) + 5. Female form: BMR = (10 × kg) + (6.25 × cm) − (5 × age) − 161. Units matter: height in centimetres, weight in kilograms. If you only know inches and pounds, convert first (or use the Unit Converter), then calculate.

Activity multipliers

TDEE ≈ BMR × activity factor. Common factors are sedentary ≈ 1.2, light ≈ 1.375, moderate ≈ 1.55, active ≈ 1.725, and very active ≈ 1.9. The biggest user error is optimism: desk work with two gym sessions is usually “light” or “moderate,” not “very active.”

If weight trends up while you eat at “maintenance,” your activity factor is probably too high or portions are undercounted. Adjust by about 100–200 kcal and reassess over one to two weeks rather than rewriting your whole plan every day.

Goals: loss, maintain, gain

A moderate deficit (often around 300–500 kcal below TDEE) is a common sustainable weight-loss starting point for many healthy adults. A similar surplus can support gradual gain. Aggressive cuts look faster on paper and fail more often in real life because adherence collapses.

ShishwaLab applies a modest ±350 kcal goal offset as a planning hint. It is not individualized medical nutrition therapy. Pregnancy, clinical conditions, disordered eating history, and athletic peaking all need professional guidance.

Worked example

A 30-year-old male, 175 cm, 70 kg: BMR ≈ 10×70 + 6.25×175 − 5×30 + 5 = 1,648.75 kcal (about 1,649). With moderate activity (×1.55), TDEE ≈ 2,556 kcal. A mild loss target might sit near 2,200 kcal; maintenance near 2,556; a mild gain near 2,900. Female estimates use −161 instead of +5 and will land lower for the same age/height/weight.

How to use the calculator well

• Enter accurate height and weight; small unit mistakes create large calorie errors.
• Pick the activity level that matches your week, not your best week.
• Track weight and energy for 1–2 weeks before large changes.
• Pair BMR/TDEE planning with the BMI tool for context, not as a diagnosis.
• Treat outputs as estimates for healthy adults, not prescriptions.

Bottom line

Mifflin-St Jeor gives a resting baseline; activity factors turn that into a daily budget; goals nudge the budget up or down. Use the numbers as a starting map, then let real-world trend data steer the next adjustment.