To what precision should percent maximum density be reported?

• A. Nearest whole percent
• B. Nearest tenth of a percent
• C. Nearest two percent
• D. No rounding

Answer: (A)

Percent maximum density represents how close the soil is to its highest achievable density based on the standard compaction tests. Because both lab and field density measurements have inherent variability, the results are reported with practical accuracy: to the nearest whole percent. This level of precision matches how specifications and QA tolerances are written and prevents implying a false level of exactness. Reporting to the nearest tenth of a percent would suggest more precision than the measurements justify, while any level of rounding beyond a whole percent isn’t necessary for the typical acceptance decisions. So, the best choice is reporting to the nearest whole percent.