k (λ, W/m·K) is the material property: how readily heat conducts through it, independent of thickness, but dependent on temperature. R (m²·K/W) is the assembly property: thickness ÷ k for a flat layer — what a given construction actually resists. Industrial practice quotes λ at mean temperature because the same product has very different λ at 10 °C and at 300 °C mean; building practice quotes R because constructions are standardized. For pipes neither tells the whole story: cylindrical geometry means each added millimetre adds less resistance and more surface — which is why pipe tables (like the ones on this site) are computed, not converted.
Compute your own case: free heat-loss calculator · materials library: 12 datasheets · related: What is CUI (corrosion under insulation)? · What is economic thickness of insulation? · What insulation works at 600 °C? · Can insulation touch the hot pipe directly?
