In practice, there is the lack of a simple algorithm derived from the theory of the uncertainty for the development of the measurement results for concrete compression strength. The article presents several variants for estimating the uncertainty of measurement results of the surface pressure for cylindrical samples and their average compression strength. Developed formulas deal with standard cylindrical samples and core samples coming from walls in concrete construction. In addition, it has been shown what is the impact of adopting the accuracy of the mathematical constant,π and measured diameter on the uncertainty results of the cross-sectional area of cylindrical samples, and consequently also the results of the average compressive concrete strength. Presented analysis showed that during application of typical compression machines (class 0.5 and 1) in concrete study the uncertainty of designated strength depends mainly on the accuracy in measuring the diameter of the samples and the accuracy of the determination of the surface pressure. In the light of the above, the guidelines contained in the standards for determining the diameter of the samples with an accuracy of 0.5% size (e.g. 100 mm ±0.5 mm) and determination based on the cross-sectional area – is insufficient. In the case of samples having a diameter at least 100 mm, it is recommended to set it with an accuracy of ±0.1 mm using resolution of calipers 0.01 mm.

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