The answer depends on what information about the body you do have.
"A BMI scale is used to calculate BMI or Body Mass Index; additionally, a BMI chart, formula, or a standard BMI calculator may be used to calculate BMI or Body Mass Index as well."
You can calculate the mass of an object by multiplying its density by its volume. The formula to calculate mass is: mass = density x volume.
mass/volume
density = mass/volume
You would need to know the density of the object in order to calculate the volume from the mass. The formula to calculate volume from mass and density is: Volume = Mass / Density.
The formula to calculate force in newtons is force mass x acceleration.
To find the density of your body, you would measure your body's mass using a scale and then calculate your body's volume by measuring its dimensions and using the appropriate formula (e.g., water displacement method). The density of your body is then calculated by dividing the mass by the volume.
BMI is a measure that is calculated by dividing body mass by the square of the height. The body mass index is easier to calculate by using a BMI calculator
The force with which gravity attracts a body is called weight. It depends on the mass of the body and the acceleration due to gravity. The formula to calculate weight is weight = mass x acceleration due to gravity.
Mass of a body and its speed are needed to calculate kinetic energy. Kinetic energy of an object = mv2/2 This formula is useful only when object's speed is much less than speed of light.
The formula used to calculate force is: Force = mass x acceleration. This formula describes how a force is generated when an object with mass is accelerated.
weight=mass*gravity