Average Percentage Calculator
Find the correct average of two percentages, weighted by their sample sizes.
Averaging percentages by simply adding and halving is usually wrong — you must weight each by how many items it represents.
How the Math Works
The Average Percentage Calculator uses a weighted average formula to combine two percentages accurately. Instead of simply averaging p1 and p2, it multiplies each percentage by its corresponding sample size (n1 and n2) to account for the relative importance of each data point. The formula weighted = (p1·n1 + p2·n2) ÷ (n1 + n2) ensures that larger samples have more influence on the final result, providing a mathematically correct average that reflects the true proportion across combined datasets.
Practical Applications
To apply this calculation, enter the first percentage value and its sample size, then input the second percentage and its sample size. For example, if you surveyed 50 people with 60% satisfaction and 100 people with 40% satisfaction, the calculator determines the overall satisfaction rate. Simply input p1=60, n1=50, p2=40, n2=100 to get the weighted average, which correctly accounts for the larger group's influence on the total result.
Day-to-Day Use
This calculator is invaluable for everyday financial and business decisions. It helps you calculate average interest rates across different savings accounts, determine overall product ratings from reviews of varying sample sizes, or compare performance metrics across different time periods. Whether you're evaluating survey results, analyzing investment returns, or assessing customer feedback, this tool provides the accurate average percentage you need to make informed decisions with confidence.
Worked example
40% of 50 and 80% of 150 → (20 + 120) ÷ 200 = 70%, not the naive 60%.
FAQ
When is the simple average correct?
Only when both groups have the same sample size.