A neuromodulation system, comprising: a plurality of electrical terminals respectively configured to be electrically coupled to a plurality of electrodes implanted within a target tissue site; modulation output circuitry coupled to the plurality of electrical terminals to deliver electrical modulation energy to the target tissue site of the patient at a programmed intensity value, thereby providing therapy to the patient without perception of stimulation; monitoring circuitry coupled to the plurality of electrical terminals; and control/processing circuitry configured to: (i) initiate a calibration of the sub-perception therapy in response to an event to determine a perception threshold and compute, as a function of the perception threshold, an intensity value to be used in the sub-perception therapy, wherein the control/processing circuitry is configured to: direct, in response to the event, the modulation output circuitry to deliver electrical modulation energy at a series of incrementally increasing intensity values relative to the programmed intensity value; prompt the monitoring circuitry to sense at least one evoked compound action potential (eCAP) indicative of the perception threshold in a population of neurons in the target tissue site of the patient in response to the delivery of the electrical modulation energy at the series of incrementally increasing intensity values; select one of the series of incrementally increased intensity values corresponding to the at least one sensed eCAP indicative of the perception threshold; and automatically compute a decreased value as a function of the selected intensity value; and (ii) direct the modulation output circuitry to deliver electrical modulation energy to the target tissue site of the patient at the computed intensity value to provide the sub-perception therapy. a plurality of electrical terminals respectively configured to be electrically coupled to a plurality of electrodes implanted within a target tissue site; modulation output circuitry coupled to the plurality of electrical terminals to deliver electrical modulation energy to the target tissue site of the patient at a programmed intensity value, thereby providing therapy to the patient without perception of stimulation; monitoring circuitry coupled to the plurality of electrical terminals; and control/processing circuitry configured to: (i) initiate a calibration of the sub-perception therapy in response to an event to determine a perception threshold and compute, as a function of the perception threshold, an intensity value to be used in the sub-perception therapy, wherein the control/processing circuitry is configured to: direct, in response to the event, the modulation output circuitry to deliver electrical modulation energy at a series of incrementally increasing intensity values relative to the programmed intensity value; prompt the monitoring circuitry to sense at least one evoked compound action potential (eCAP) indicative of the perception threshold in a population of neurons in the target tissue site of the patient in response to the delivery of the electrical modulation energy at the series of incrementally increasing intensity values; select one of the series of incrementally increased intensity values corresponding to the at least one sensed eCAP indicative of the perception threshold; and automatically compute a decreased value as a function of the selected intensity value; and (ii) direct the modulation output circuitry to deliver electrical modulation energy to the target tissue site of the patient at the computed intensity value to provide the sub-perception therapy. (i) initiate a calibration of the sub-perception therapy in response to an event to determine a perception threshold and compute, as a function of the perception threshold, an intensity value to be used in the sub-perception therapy, wherein the control/processing circuitry is configured to: direct, in response to the event, the modulation output circuitry to deliver electrical modulation energy at a series of incrementally increasing intensity values relative to the programmed intensity value; prompt the monitoring circuitry to sense at least one evoked compound action potential (eCAP) indicative of the perception threshold in a population of neurons in the target tissue site of the patient in response to the delivery of the electrical modulation energy at the series of incrementally increasing intensity values; select one of the series of incrementally increased intensity values corresponding to the at least one sensed eCAP indicative of the perception threshold; and automatically compute a decreased value as a function of the selected intensity value; and direct, in response to the event, the modulation output circuitry to deliver electrical modulation energy at a series of incrementally increasing intensity values relative to the programmed intensity value; prompt the monitoring circuitry to sense at least one evoked compound action potential (eCAP) indicative of the perception threshold in a population of neurons in the target tissue site of the patient in response to the delivery of the electrical modulation energy at the series of incrementally increasing intensity values; select one of the series of incrementally increased intensity values corresponding to the at least one sensed eCAP indicative of the perception threshold; and automatically compute a decreased value as a function of the selected intensity value; and (ii) direct the modulation output circuitry to deliver electrical modulation energy to the target tissue site of the patient at the computed intensity value to provide the sub-perception therapy.