Weld joints play a very important role in assessment of structural integrity of steel structures. The weld joint region is the location of weld induced residual stress and strain fields (WRS). For the time being there is a lack of engineering methods to be used for approximations of the maximum WRS magnitudes in the way of a weld joint proposed to be produced with a specific Welding Procedure Specification (WPS). Or screening of residual stress measurement results obtained by various measuring methods. This report describes how one can proceed to establish best estimate material data by the use of the Meyer’s hardness. The Meyer’s hardness can also be used to determine the maximum physically possible WRS magnitude.