How do you calculate mass using Newton's 2nd Law?

To calculate from the mass by the during Newton's 2nd law are:

Newton's second law of motions is a states that the total net force will be acting on an object is to equal by the mass times acceleration.

With formula of m=f/a or a=f/m, and F=ma

The 2nd Law says F=ma, where F is the force in Newtons, m is mass and a is acceleration. Earth's gravity is an acceleration, 9.8m/s^2. So you can solve the equation for mass, m=F/a, or m=F/9.8 where you've measured the force (weight) in Newtons.