Abstract: A method for evaluating uncertainty associated with the value of a measurand derived from measurements of a device under test is disclosed. A mathematical model is provided wherein the measurand is expressed as a function of (i) at least one physically observable quantity, and (ii) the reference value of the physically observable quantity in a reference device. The reference value of the reference device and the value of the measurand of the device under test are measured. The value of the at least one physically observable quantity is also measured. At least one uncertainty value is determined as a function of the physically observable, wherein the mathematical model takes into account the at least one source of uncertainty and the reference value of the reference device.