actually i find the area by using indirect way. I put a linear to the curve which has same area (seems like it has same area). Then i obtain the area under the curve by using triangle area formula from the linear which i added to curve.

Is there any simple way to obtain area under the curve?

Well, if a linear fit fits it well, use a trapezoidal approximation
or just use rectangles, easiest way

I'm pretty sure excel can only do numerical integration
so, even if you had a defined function, it would not integrate it

This post was edited by saber_x3 on Dec 24 2013 11:39am

thanks guys you helped a lot^^ it was so easy