For extremely large datasets, you can improve calculation speed by disabling automatic calculation. Go to the Excel Options menu, select Formulas, and choose the option to manually calculate. This allows you to control when the calculations take place and can significantly speed up performance for complex worksheets with many calculations.

Another approach is to use the AutoSum feature in Excel. Select the cell where you want the sum to appear, then click on the AutoSum button (∑) in the toolbar. Excel will automatically detect the range of numbers adjacent to the selected cell and populate the formula for you. This is particularly useful when dealing with large sets of data or when the range is not continuous.

One efficient way to calculate the sum of a large range of numbers in Excel is to use the SUM function with a colon operator. For example, if you want to sum up numbers from A1 to A100, you can simply use the formula =SUM(A1:A100). This method avoids the need for manually typing out each cell reference and ensures accuracy.