A method of ablation includes storing in a memory a pre-determined relation between lesion size and amount of ablative energy, for each of one or more selected temperatures. Using a processor, user input is received, that indicates a lesion size and a tissue temperature. Based on the relation, an amount of energy is determined, that matches the lesion size and the tissue temperature. An ablation probe is controlled to apply the amount of ablative energy that matches the selected lesion size.
