This article describes the formula syntax and usage of the ROUNDDOWN function in Microsoft Excel.
Description
Rounds a number down, toward zero.
Syntax
ROUNDDOWN(number, num_digits)
The ROUNDDOWN function syntax has the following arguments:

Number Required. Any real number that you want rounded down.

Num_digits Required. The number of digits to which you want to round number.
Remarks

ROUNDDOWN behaves like ROUND, except that it always rounds a number down.

If num_digits is greater than 0 (zero), then number is rounded down to the specified number of decimal places.

If num_digits is 0, then number is rounded down to the nearest integer.

If num_digits is less than 0, then number is rounded down to the left of the decimal point.
Example
Copy the example data in the following table, and paste it in cell A1 of a new Excel worksheet. For formulas to show results, select them, press F2, and then press Enter. If you need to, you can adjust the column widths to see all the data.
Formula 
Description 
Result 
=ROUNDDOWN(3.2, 0) 
Rounds 3.2 down to zero decimal places. 
3 
=ROUNDDOWN(76.9,0) 
Rounds 76.9 down to zero decimal places. 
76 
=ROUNDDOWN(3.14159, 3) 
Rounds 3.14159 down to three decimal places. 
3.141 
=ROUNDDOWN(3.14159, 1) 
Rounds 3.14159 down to one decimal place. 
3.1 
=ROUNDDOWN(31415.92654, 2) 
Rounds 31415.92654 down to 2 decimal places to the left of the decimal point. 
31400 