Maryam Sami Please, read:

Blanco, Flávio Favaro, and Marcos Vinícius Folegatti. "A new method for estimating the leaf area index of cucumber and tomato plants." Horticultura Brasileira 21 (2003): 666-669.

Lee JM, Jeong JY, Choi HG. Estimation of leaf area using leaf length, leaf width, and lamina length in tomato. Journal of Bio-Environment Control. 2022 Oct 31;31(4):325-31.

BEYHAN M, Sezgin UZ, KANDEMİR D, Harun ÖZ, DEMİRSOY M. A model for predicting leaf area in young and old leaves of greenhouse type tomato (Lycopersicon esculentum, Mill.) by linear measurements. Anadolu Tarım Bilimleri Dergisi. 2008 Jan 12;23(3):154-7.

The last one describes this relation as:

Equation 1 "mean leaflet length (MLL) of a main compound tomato leaf and the length of the longest leaflet (LLL) of the top three leaflets of the main compound leaf (MLL(cm)=-0.36+1,02*LLL–0,02*LLL2,

r2=0.98,.

(Equation 2 "mean leaflet length (MLL), longest leaflet length of the top three leaflets of the main leaf (LLL) and longest leaflet width (LLW) of the top three leaflets The leaf area was found as LA (cm2) =31,6–18.41*MLL+2.40*MLL2+0.45*LLL2*LLW,

r2=0.99"

Equation 3 " LA=31.6–18.41*(-0.36+1.02*LLL–0.02*LLL2)+2.40*(-0.36+1.02*LLL–0.02*LLL2) 2 +0.45*LLL2*LLW"