Fire simulators allow predicting fire spread and behavior and some of which in real-time. Both strategies and tactics to suppress wildland fires depend on fire analysis which is generally based on fire simulations that need to be accurate for a proper decision making. However, limitations and assumptions of the fire models and uncertainties in input data may induce errors in the simulated fire growth and, therefore, fire simulations do not always match actual fire spread. In this paper, we show an innovative method implemented in Wildfire Analyst to adjust fire simulations in real-time. The method determines the adjustment factors needed for the optimal rate of spread by fuel model in order to minimize the arrival time error between the simulated fire and a set of control points where the arrival time of the observed (real) fire is known. Two case studies were used to present the method, showing robust results in reducing the error and fitting the simulated fire growth to the real fire spread, with practical real-time implications. The method presented may be solved in real-time and used with any empirical fire propagation.