We aimed to monitor greenhouse tomato growth without destructive sampling and investigated an empirical growth model in which dry matter production was obtained as a product of light intercepted by plants and light-use efficiency. The intercepted light values were non-destructively determined on the basis of leaf width and length, and the number of leaves. Light-use efficiency was expressed as a function of daytime CO₂ concentration. Three cultivation experiments were conducted with three tomato cultivars over two years. Significant regression lines and curves, as well as coefficients of the model, were obtained for each cultivar. Using photosynthetic curves of the three cultivars and solar radiation data, we suggest an approach to determine the recommended leaf area index to maximize dry matter production. The developed model has potential to improve yield and labor efficiency in tomato production.