You need to get: A. Sesay & H. Zungu. Estimating Leaf Area Per Plant in Bambara Groundnut (Vigna subterranean) Using Leaf Number and Leaf Dry Weight. UNISWA Research Journal of Agriculture, Science and Technology Vol 3 (2) 2000: pp 63-65.

Unfortunately I do not have access to the full article, but the answer you need is in there.

Hi Aleksandra Maljković ,

Thanks for the answer. But I need to know about peanut (Arachis hypogea).

Hi, maybe what you are looking for is here. See the table 4. It provides one idea, valid in this experimental conditions, but depending of the desired accuracy you can use this value.

naldc.nal.usda.gov/download/38837/PDF

Dear Dr. Marcelo Corrêa Alves,

Thank you so much :)