BMR for Weight Gain Calculator

Calculator inputs

Unit system

Formula

Sex

Age

Weight (kg)

Height (cm)

Body fat % (needed for Katch-McArdle)

Activity level

Surplus mode

Desired weekly gain

Metric uses kg/week. Imperial uses lb/week.

Protein target (g/kg)

Fat share of calories (%)

Meals per day

Formula used

BMR formula options

Mifflin-St Jeor (male) = 10W + 6.25H − 5A + 5

Mifflin-St Jeor (female) = 10W + 6.25H − 5A − 161

Revised Harris-Benedict (male) = 88.362 + 13.397W + 4.799H − 5.677A

Revised Harris-Benedict (female) = 447.593 + 9.247W + 3.098H − 4.330A

Katch-McArdle = 370 + (21.6 × lean body mass in kg)

Maintenance calories: TDEE = BMR × activity factor.

Automatic weight gain surplus: Daily Surplus = (desired weekly gain in kg × 7700) ÷ 7.

Target calories: Target = maintenance + daily surplus.

Protein: Protein grams = body weight in kg × chosen protein target.

Fat: Fat grams = (target calories × fat percentage) ÷ 9.

Carbohydrates: Carb grams = remaining calories ÷ 4 after protein and fat calories are assigned.

The 7700 kcal per kilogram rule is a practical estimate, not a guarantee. Real weight change varies with training, stress, hydration, sleep, digestion, and adherence.

How to use this calculator

Select metric or imperial units.
Choose your preferred BMR equation.
Enter age, sex, body size, and activity level.
Add body fat if you use Katch-McArdle.
Choose automatic gain pacing or set a custom surplus.
Set protein, fat percentage, and meals per day.
Press Calculate to show calories, macros, and projected gains above the form.
Use the chart and export buttons to save your result.

Example data table

Profile	Formula	Activity	BMR	Maintenance	Target	Protein
Male, 28, 70 kg, 175 cm	Mifflin-St Jeor	Moderate	1649 kcal	2556 kcal	2831 kcal	126 g
Female, 32, 60 kg, 165 cm	Revised Harris-Benedict	Light	1386 kcal	1906 kcal	2156 kcal	108 g

These sample values illustrate how the calculator presents outputs. Your own results change with formula choice, body size, activity, and selected surplus.

FAQs

1. Which BMR formula should I choose?

Mifflin-St Jeor is a strong default for most adults. Revised Harris-Benedict is another common estimate. Katch-McArdle is useful when you know body fat percentage and want a lean-mass-based calculation.

2. What is the difference between BMR and maintenance calories?

BMR estimates calories burned at complete rest. Maintenance calories include movement, exercise, digestion, and daily activity. Maintenance is usually much higher than BMR.

3. How much daily surplus is reasonable for gaining weight?

A moderate surplus often works best. Small surpluses usually support slower gains with less unwanted fat. Larger surpluses can speed results, but body composition may be less favorable.

4. Why does the calculator ask for protein and fat settings?

Calories set the overall energy target, but macros shape meal planning. Protein supports recovery and muscle gain, fat supports hormones, and carbohydrates fill the remaining energy needs.

5. Is the projected weekly gain guaranteed?

No. It is an estimate based on calorie math. Real-world progress changes with training quality, consistency, sleep, hydration, food tracking accuracy, and individual metabolism.

6. Should I use Katch-McArdle without a body fat estimate?

Not ideally. Katch-McArdle depends on lean body mass, so body fat must be reasonably estimated. If you do not know body fat, use Mifflin-St Jeor instead.

7. Can this calculator help with lean bulking?

Yes. Choose a smaller gain rate or a modest custom surplus, keep protein adequate, and review your progress every few weeks to adjust calories as needed.

8. How often should I recalculate my targets?

Recalculate whenever body weight, activity, training volume, or goals change meaningfully. Many people review their targets every two to four weeks during a focused gaining phase.