utilduck uses primary sources for the numbers and reference tables in its calculators — government agencies, standards bodies, and official documents. We do not build the figures a tool relies on from secondhand summaries or unverified aggregator data.
When we cannot confirm a value against a primary source, we leave it out of the table or describe it in the text instead of publishing a fabricated number.
Look for the "Sources" section at the bottom of each tool page — it links directly to the original document from the relevant agency or organization.
Examples of primary sources actually used on utilduck:
- WHO Child Growth Standards
- FDA unit conversion guidance (2019)
- NOAA heat index (Rothfusz regression)
- National nutrient intake standards — US DRI, Korea's KDRIs, Japan's 食事摂取基準, and the EU's EFSA DRVs
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See How calculations work for how each tool turns these sources into a result.