Calculator21

Formula:
Mifflin-St Jeor Equation:
For men:           BMR = 10W + 6.25H - 5A + 5
For women:      BMR = 10W + 6.25H - 5A - 161

where:
W is body weight in kg
H is body height in cm
A is age

Multiplying the BMR by the appropriate activity factor:
Sedentary - BMR × 1,2 (little to no exercise, desk job)
Light Activity - BMR × 1.375 (exercise 1 to 3 days per week)
Moderate Activity - BMR × 1,55 (exercise 3 to 5 days per week)
Very Active - BMR × 1.725 (exercise 6 to 7 days per week)
Extra Active - BMR × 1,9 (exercise 2x per day)

Source:
https://pubmed.ncbi.nlm.nih.gov/15883556/
https://pubmed.ncbi.nlm.nih.gov/2305711/