Standard Deviation Calculator

This tool measures how spread out a set of numbers is from its average, which is useful for analyzing test scores, measurements, financial returns, or any dataset where you want to understand consistency versus variability.

It first finds the mean by averaging all your values, then calculates how far each value deviates from that mean, squares those differences (so negatives don't cancel out), averages the squared differences to get variance, and takes the square root to return to the original units as standard deviation.

Example: For the dataset 2, 4, 4, 4, 5, 5, 7, 9, the mean is 5. Squaring and averaging the deviations gives a population variance of 4, so the population standard deviation is √4 = 2 — meaning most values typically fall within 2 points of the average.