Sources and methodology
How averagecalculator.io chooses formulas, which references we check them against and how each calculator is tested before it goes live.
Last updated: September 20, 2026
In short
- Each calculator uses the standard formula for its job, written out on the page.
- Results are checked against hand-worked examples and spreadsheet functions such as AVERAGE, MEDIAN and SUMPRODUCT.
- Every tool is tested with awkward inputs like blanks, zeros, negative numbers and times that cross midnight.
- A second expert reviews each tool before it goes live.
Why we publish our methods
A calculator can look right and still be wrong. The wrong divisor, or percentages averaged the simple way, gives a number that looks reasonable and isn’t. Publishing how we test our tools lets you check our work instead of taking it on trust.
How we choose a formula
For every calculator we write down:
- what exactly is being calculated
- the formula, with every term defined
- any version that gives a different answer, and which one we use
- where the formula stops working
- how the input should be read, for example whether 1:30 means minutes or hours
When two methods are both valid, the page says which one the calculator uses and why.
References we check against
- NIST/SEMATECH e-Handbook of Statistical Methods, for definitions of the mean, median, mode and related measures
- Microsoft Excel function documentation, for AVERAGE, MEDIAN, MODE, SUMPRODUCT and related functions
- Google Sheets function list, for the same functions in Sheets
- Standard statistics textbooks used in introductory university courses
Other calculator websites and forums are never used as the source of a formula.
How we test each calculator
The site covers statistics only. Below are the calculators live today. Each new statistics calculator is added to this list with its own tests when it launches.
Average calculator
The mean, median and mode are compared with AVERAGE, MEDIAN and MODE in Excel for lists of different lengths. We test lists with an even count, where the median is the average of the two middle values, lists with more than one mode and lists where no value repeats.
Weighted average calculator
Every result is compared with =SUMPRODUCT(values, weights)/SUM(weights). We test weights that add up to 100, weights that add up to 1 and weights that add up to neither, because the calculator divides by the total weight and should give the same answer in all three cases.
Average percentage calculator
Averaging percentages the simple way is often wrong. If you scored 80% out of 50 and 60% out of 200, your overall score is 64%, not 70%. We test that the calculator weights each percentage by its total when you fill in the “Out of” column, and gives a simple average when you leave it empty.
Average time calculator
We test hours, minutes and seconds in different formats, including 1h 30m, 1:30:00 and 90 minutes. Because 1:30 can mean 1 minute 30 seconds or 1 hour 30 minutes, you can choose how it is read. For clock times, we test lists that cross midnight: the average of 11:30 PM and 12:30 AM should be 12:00 AM, not 12:00 PM.
Edge cases
Every tool is tested with empty fields, a single value, zeros, negative numbers, decimals, very large numbers and text typed where a number should go. The calculator must give the correct result or a clear message. A wrong answer with no warning counts as a bug.
Rounding
Rounded results are compared with the spreadsheet result to the same number of decimal places. The steps show the values used, so you can follow the calculation.
When something changes
If we change a formula, add a feature or fix an error, the calculation, worked examples and explanation are updated together and the page’s updated date changes. Confirmed errors that could have affected results are noted on the page.
What a calculator can and cannot tell you
An average is one number standing in for many. It can hide a lot, and a single outlier can pull the mean far from a typical value. Our calculators give accurate results for the numbers you enter, but they cannot tell whether an average is the right measure for your situation. The explanation on each page covers when to use the mean, median or a weighted average. For grades, check your school’s own rules, since some schools round or weight differently.
Your numbers stay on your device
Calculations run in your browser. The numbers you type are not sent to our server and are not saved. See our privacy policy for details.
Report an error
Think a result is wrong? Use the Report an error link on the calculator, or email [email protected] with the numbers you entered, the result you got and the result you expected. Our editorial policy explains how corrections are handled.