This study presents predictions of a comprehensive numerical model for the burning characteristics of laminar flames over MMA pools of different diameters with varying ullages or lip heights. Numerical results have been validated using the measurements from lab-scale experiments for steady burning of MMA pool, conducted by researchers at Siberian Branch Russian Academy of Sciences, Russia. The temperature and concentrations of major species have been measured for 3 mm ullage case for pool diameters of 25 and 30 mm. A compact kinetic mechanism with 49 species and 376 reactions, and a soot model are used for numerical simulations. Steady burning of laminar flame over an MMA pool is modelled using coupling heterogeneous interface conditions. Variable thermo-physical properties and multi-component diffusion are used. Results from grid-independent numerical simulations compare with reasonable accuracy against experimental measurements. For a 25 mm MMA pool, the mass burning rate decreases rapidly from zero to 2 mm ullage and drops relatively gradually with further increase in the ullage. The ratio of mass of soot in the domain to mass of fuel burnt, decreases rapidly with an increase in ullage from zero to 3 mm, remains in same order till 5 mm ullage and then decreases with increasing ullage. Increased flame stand-off from the pool interface and oxygen penetration into the ullage causing partial premixing, form the reasons for the reduction in mass burning rate and decrease in the production of soot. The effects of pool diameter on burning characteristics at three ullages have also been presented.