Data Sources and Methodology
Understanding how we gather, process, and present nutrition information.
Primary Data Source: USDA FoodData Central
Most nutrition data on CalorieData is sourced from the USDA FoodData Central database, maintained by the U.S. Department of Agriculture. This is the authoritative source used by healthcare professionals, registered dietitians, researchers, and food manufacturers worldwide.
FoodData Central is developed by the Agricultural Research Service (ARS), the chief scientific in-house research agency of the USDA. The database contains comprehensive nutrient profiles for hundreds of thousands of foods, of which we publish a curated set of 500+ pages.
Our secondary source: manufacturers' product labels. Not every food we cover has a FoodData Central record — this is common for branded packaged goods and restaurant menu items. For those entries we compile the values from the manufacturer's own published Nutrition Facts panel. Roughly 197 of our 529 food records are tied to a verified FoodData Central record and link directly to it; the other 332 are label-derived and are labeled “Compiled from product label” on the page. We do not present label-derived numbers as USDA data.
USDA Database Components
The USDA FoodData Central integrates data from multiple specialized sources:
SR Legacy (Standard Reference)
The foundational database containing comprehensive nutrient profiles for over 7,000 generic foods, developed over decades of laboratory analysis.
Foundation Foods
Enhanced nutrient data using state-of-the-art analytical methods, providing the most accurate values available for key reference foods.
FNDDS
Food and Nutrient Database for Dietary Studies, containing detailed information on mixed dishes and recipes used in national nutrition surveys.
Branded Foods
Nutrition data submitted directly by food manufacturers for branded and packaged products through the Global Branded Food Products Database.
How Nutritional Values Are Calculated
Calorie Calculation (Atwater System)
Calorie values for our USDA-sourced entries come directly from USDA laboratory analysis; label-derived entries use the calorie figure the manufacturer prints. The USDA uses the Atwater system, the internationally accepted method that calculates food energy based on digestible macronutrient content:
- Protein: 4 calories per gram
- Carbohydrates: 4 calories per gram
- Fat: 9 calories per gram
- Alcohol: 7 calories per gram (when present)
Some foods use modified Atwater factors that account for differences in digestibility. The USDA applies these adjustments where scientific evidence supports their use.
Standardization to 100 Grams
All nutrition information on CalorieData is standardized to per 100 gram servings as the primary reference. This allows for accurate, apples-to-apples comparisons between any foods in our database.
Serving Size Calculations
We provide nutrition facts for common serving sizes (cups, tablespoons, pieces, slices, etc.) calculated using USDA standard reference portions and gram weights. The formula is:
Rounding Conventions
Following FDA labeling guidelines:
- Calorie values are rounded to the nearest whole number
- Macronutrients (protein, carbs, fat) are rounded to one decimal place
- Micronutrients are rounded appropriately based on their typical ranges
Data Quality and Accuracy
Quality Assurance
We implement multiple layers of quality assurance to ensure data accuracy:
- Source Verification: Every record that we credit to the USDA carries an FDC ID that we have confirmed resolves to a matching FoodData Central entry, and each such page links to that record so you can check it yourself. Records without a confirmed FDC ID carry no FDC ID at all and are shown as label-derived rather than USDA data.
- Automated Validation: Our import process checks for anomalous values that may indicate data errors (e.g., calorie values that do not match calculated macronutrient totals).
- Manual Review: High-traffic food pages are periodically audited against source data.
- User Feedback: We maintain a system where users can report suspected errors for investigation.
Handling Missing Data
When specific nutrient data is not available for a food in the USDA database, we clearly indicate this rather than displaying zeros, which could be misleading. Some nutrients may show as "N/A" or not be displayed when data is unavailable.
Update Frequency
Maintaining current, accurate nutrition data is essential to our mission:
- USDA Data Sync: We re-check our USDA-sourced records against FoodData Central when new data releases are published, and drop the USDA credit from any record whose FDC ID no longer resolves.
- Branded Food Updates: Branded food products are updated as manufacturers submit new information to the USDA.
- Error Corrections: Verified errors are corrected within 5 business days of confirmation.
Important Limitations
While we strive for accuracy, there are inherent limitations to nutrition data:
- Natural Variation: Nutritional values for whole foods can vary based on growing conditions, ripeness, variety, and season.
- Preparation Methods: Cooking methods can significantly alter nutrient content. Our values typically represent raw or standardized preparation unless otherwise noted.
- Branded Product Changes: Manufacturers may reformulate products, causing temporary discrepancies until databases are updated.
- Serving Size Estimates: Actual serving sizes may vary from standardized portions used in calculations.
- Individual Absorption: How your body absorbs and utilizes nutrients can vary based on individual factors.
The values provided should be used as general guidelines rather than exact figures. For precise dietary management, especially for medical conditions, consult with a registered dietitian or healthcare provider.
Official USDA Resources
For those who wish to access the source data directly or learn more about USDA nutrition databases:
Questions About Our Data?
If you have questions about our methodology, notice potential data errors, or want to learn more about how we process nutrition information, please contact us at contact@caloriedata.org.
We investigate all reported discrepancies and work to maintain the highest standard of data accuracy.