A new method of measuring heat flux from smoldering combustion is introduced. Currently available methods lack the accuracy of measuring the true heat flux. This is because of either the unavailability of required physical properties of the transporting medium (Like time dependent thermal conductivity) and/or failing to incorporate the transport of heat by mass transfer. In the present method, these difficulties are overcome. A dewar (calorimeter) placed below the fuel bed captured the water vapor and thus the heat of condensation released to the water in the dewar. The rate of temperature rise of the water in the dewar is a measure of the heat flux from the fuel bed. Integration of the heat flux over time divided by the capture cross-section area of the dewar opening yields the heat load (heat per unit area) falling on the calorimeter. Availability of an accurate method to measure heat flux from smoldering combustion has many practical applications, especially in forest fire situations.