# Dart: Calculating Variance and Standard Deviation

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**Variance** is a statistical measure that quantifies the amount of variability or spread in a set of data. It is calculated as the average of the squared differences from the mean of the data.

**Standard deviation** is the square root of the variance and is another statistical measure of the amount of variability in a set of data. It tells you how much the data deviates from the mean, on average.

In Dart, you can calculate the **variance** and **standard deviation** of a list of numbers like this:

```
// Kindacode.com
// main.dart
import 'dart:math';
void main() {
List<double> data = [0.5, 1.1, 3, 4, 5, 10, 11, 9, 7.4, 8.2];
// Calculate the mean
double mean = data.reduce((a, b) => a + b) / data.length;
// Calculate the variance
double variance = data.map((x) => pow(x - mean, 2)).reduce((a, b) => a + b) /
(data.length - 1);
// Calculate the standard deviation
double standardDeviation = sqrt(variance);
print('Variance: $variance');
print('Standard Deviation: $standardDeviation');
}
```

Output:

```
Variance: 13.888444444444444
Standard Deviation: 3.7267203335432137
```

If you want to round the results to 2 decimals numbers, use the **toStringFixed()** method as follows:

```
var roundedVariance = variance.toStringAsFixed(2);
var roundedStandardDeviation = standardDeviation.toStringAsFixed(2);
```

**Further reading:**

- Dart: 2 Ways to Calculate the Power of a Number (Exponentiation)
- How to add/remove a duration to/from a date in Dart
- 2 Ways to Get a Random Item from a List in Dart (and Flutter)
- How to Create a Stopwatch in Flutter
- Flutter: 2 Ways to Create an Onboarding Flow (Intro Slider)
- 2 Ways to Create Typewriter Effects in Flutter

You can also tour around our Flutter topic page or Dart topic page for the most recent tutorials and examples.