A computer implemented method of calibrating measurements made using a medical monitoring device, the method comprising: - obtaining a first conversion factor comprising a first cross correlation that describes the correlation between measurements made using a first medical monitoring device and measurements made using a second medical monitoring device; and - using the first conversion factor to convert measurements from the first medical monitoring device onto the same scale as measurements from the second medical monitoring device, wherein the step of obtaining comprises: - receiving a first set of measurements from the first medical monitoring device; - receiving a second set of measurements from the second medical monitoring device; and - computing the first cross correlation as the cross correlation between the first set of measurements and the second set of measurements, wherein the step of obtaining further comprises: - generating the first conversion factor from the first cross correlation by at least one of: adding an offset to; and scaling the first cross correlation using a scaling factor, wherein the offset and the scaling factor comprise one or more parameters relating to at least one of the first medical monitoring device and the second medical monitoring device. - obtaining a first conversion factor comprising a first cross correlation that describes the correlation between measurements made using a first medical monitoring device and measurements made using a second medical monitoring device; and - using the first conversion factor to convert measurements from the first medical monitoring device onto the same scale as measurements from the second medical monitoring device, wherein the step of obtaining comprises: - receiving a first set of measurements from the first medical monitoring device; - receiving a second set of measurements from the second medical monitoring device; and - computing the first cross correlation as the cross correlation between the first set of measurements and the second set of measurements, wherein the step of obtaining further comprises: - generating the first conversion factor from the first cross correlation by at least one of: adding an offset to; and scaling the first cross correlation using a scaling factor, wherein the offset and the scaling factor comprise one or more parameters relating to at least one of the first medical monitoring device and the second medical monitoring device. - receiving a first set of measurements from the first medical monitoring device; - receiving a second set of measurements from the second medical monitoring device; and - computing the first cross correlation as the cross correlation between the first set of measurements and the second set of measurements, wherein the step of obtaining further comprises: - generating the first conversion factor from the first cross correlation by at least one of: adding an offset to; and scaling the first cross correlation using a scaling factor, wherein the offset and the scaling factor comprise one or more parameters relating to at least one of the first medical monitoring device and the second medical monitoring device. - generating the first conversion factor from the first cross correlation by at least one of: adding an offset to; and scaling the first cross correlation using a scaling factor, wherein the offset and the scaling factor comprise one or more parameters relating to at least one of the first medical monitoring device and the second medical monitoring device. adding an offset to; and scaling the first cross correlation using a scaling factor, wherein the offset and the scaling factor comprise one or more parameters relating to at least one of the first medical monitoring device and the second medical monitoring device.