The problem of calibration in which the response variable is measured bykdifferent methods or using different instruments is considered. It is well known that the usual classical estimator for the unknown explanatory variable has infinite mean and mean squared error whenk= 1. In this article a linear combination of the classical estimators is proposed. It is shown that the combined estimator has finite mean provided thatk≥ 2 and finite mean squared error provided thatk≥ 3. Expressions for asymptotic bias and mean squared error are given. Also, two confidence sets for the unknown exploratory variable are developed sufficient conditions under which they will be finite intervals are given. The results are illustrated by a practical example.