# Calculus of Weight and mass

I am confusing about some data for calculus.

First, the equivalence of weight: 1kgf=9.8N

Second, the mass of 1 Newton is: 1N/(9.8m/s$^2$).

And finally, to get the mass of 1kgf, I have to divide by the gravity.

An example of a weight of P=10N:

P=10N$\cfrac{\text{1kgf}}{9.8N}\approx1$kgf; its mass: $m=\cfrac{P}{g}=\cfrac{1kgf}{9.8m/s^2}\approx0.1kg$

While, directly from Newtons: $m=\cfrac{10N}{9.8m/s^2}\approx1kg$

What I am doing wrong?

• It's the units. Dividing $kgf$ by $m/s^2$ doesn't give you $kg$. Aug 4, 2016 at 23:15
• I am confused. What happened if I weight 70 kg, I must say 70kgf? I mean, to get my mass, I have to divide my weight by the gravity. What is wrong?
– Isai
Aug 4, 2016 at 23:28
• OK, how about if I tell you that gravity is $1 kgf / kg$. Does that help? Aug 4, 2016 at 23:31

• Yes, thanks. I found this in Wikipedia: $1 kp=1 kgf=g_n⋅(1 kg)$. So, in my problem, I must say: $m=\cfrac{P}{g_n}=\cfrac{1 kgf}{g_n}=\cfrac{1 ·g_n⋅(1 kg)}{g_n}=1 kg$