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Exchange couplings are calculated for Li2VOSiO4 using local density approximation (LDA). From a two band tight-binding model fitted to the LDA band structure and mapped to a Heisenberg model, the in-plane and inter-plane exchange integrals are obtained. While the sum of in-plane couplings J1+J2=9.5±1.5 K and the inter-plane coupling J⊥ ~ 0.2-0.3 K agree with recent experimental data, the ratio J2/J1 ~ 12 exceeds the reported value by an order of magnitude. Using geometrical considerations, high temperature expansions and perturbative mean field theory, we show that the LDA derived exchange constants lead to a remarkably accurate description of the properties of these materials including specific heat, susceptibility and Neél temperatures.