The formula in metric units for BMI = Weight in kilograms divided by height in meters squared. In English units, the formula for BMI = Weight in pounds divided by height in inches squared multiplied by 703. In general, a BMI over 25 is now the standard to indicate a person is overweight.he formula to calculate BMI requires information about a person's height in meters and weight in kilograms. For weight in pounds and height in inches, there is a different formula but due to rounding, it may not produce the exact same results. The BMI formulas are written below: