Sum the n smallest numbers

This formula will sum the smallest 3 numbers
SUM( SMALL( B2:D5, {1,2,3} ) )

{=SUM(SMALL(CellRange, ROW(INDIRECT(Row(CellRange) & ":" & Rows(CellRange)))))}

Built-in Functions

SUM - The total of the numerical values.
SMALL - The kth smallest numerical value.
ROW - The row number of a cell reference.
INDIRECT - The value of a given cell reference specified by a text string.