Dart: Calculating the Average of Data in a List

Updated: July 28, 2022 By: A Goodman Post a comment

This practical, succinct article walks you through two examples of calculating the average of numerical data in a given list. The first example works with a simple list that contains only numbers, while the second one deals with a list of maps. No more ado; let’s get started.

List of Numbers

To find the result, just use the average getter, like so:

// kindacode.com
import 'package:collection/collection.dart';

void main() {
  final listOne = [1, 2, 3, 4, 5, 9, 10];
  final averageOne = listOne.average;
  print(averageOne);

  final listTwo = [-3, 1.4, 3.4, 9, 10, 6];
  final averageTwo = listTwo.average;
  print(averageTwo);
}

Output:

4.857142857142857
4.466666666666667

You don’t even need to calculate the sum of all elements and then divide it by the number of elements. If you want to display the results in a nicer format, see this article: Show a number to two decimal places in Dart (Flutter).

List of Maps

Let’s imagine you have a list of maps where each map contains information about a product, including product name, price, etc. The goal is to find the average price of all products. The program below demonstrates how to solve the problem:

// kindacode.com
import 'package:collection/collection.dart';

void main() {
  final products = [
    {"name": "Product One", "price": 3.33},
    {"name": "Product Two", "price": 9.99},
    {"name": "Product Three", "price": 5.00}
  ];

  // Create of list of prices
  final prices = products.map((product) => product["price"] as double).toList();

  // Use the average function to get the average price
  final averagePrice = prices.average;
  print("Average Price: $averagePrice");
}

Output: