Weighted Average in Excel
Calculate an average where each row contributes a different weight.
What this solves
Average purchase price weighted by quantity. This pattern is useful when the business question is clear but a generic tutorial is too abstract.
The rule
=SUMPRODUCT(values,weights)/SUM(weights)
=SUMPRODUCT(C2:C20,D2:D20)/SUM(D2:D20)Google Sheets: The core pattern is also usable in Google Sheets; exact function support and locale separators can differ.
Real-work checklist
- Define the business key and expected grain before writing the formula, query or markup.
- Test the pattern on a small known sample where you can verify the answer manually.
- Check missing values, duplicates and data types before trusting a large result.
- Scale to the real file or database only after the logic is proven.
Common mistake
A simple AVERAGE is wrong when quantities differ materially.