Explanation
The ROUNDDOWN function rounds a number down to a given number of places. The number of places is controlled by the number of digits provided in the second argument ( num_digits ). For example, these formulas round the number 5.89 down to 1 and zero places:
=ROUNDDOWN(5.89,1) // returns 5.8
=ROUNDDOWN(5.86,0) // returns 5
In the example shown, the formula in cell D7 is
=ROUNDDOWN(B7,C7)
This tells Excel to take the value in B7 (1999.9985) and round it to the number of digits in cell C7 (2) with a result of 1999.99 Notice that even though the number in the 3rd position to the right of the decimal is 8, it is still rounded down .
In the table, the ROUNDDOWN function is used to round the same number (1999.9985) to a decreasing number of digits, starting at 2 and moving down past zero to -3. Note that positive numbers round to the right of the decimal point, while digits specified less than or equal to zero round to the left. At each step, numbers that would normally be rounded up are rounded down.
You can see that ROUNDDOWN is a rather heavy handed function, so use it carefully. You can use the FLOOR function to round a number down to a given multiple. If you want to discard the decimal portion of a number, you can use the TRUNC function .
Explanation
The Excel FLOOR function rounds a number down to a given multiple. The multiple to use for rounding is given as the second argument ( significance ). If the number is already an exact multiple, no rounding occurs. FLOOR works like the MROUND function , but unlike MROUND, which rounds to the nearest multiple, FLOOR always rounds down to the given multiple.
In the example shown, the formula in cell D6 is
=FLOOR(B6,C6)
This tells Excel to take the value in B6 ($33.39 ) and round it down to the nearest multiple of the value in C6 (5). The result is $30.00, since 30 is nearest multiple of 5 below 33.39. Likewise, in cell D7, we get 30 when rounding down using a multiple of 10.
You can use FLOOR to round prices, times, instrument readings or any other numeric value.
FLOOR rounds down using the multiple supplied. You can use the MROUND function to round to the nearest multiple and the CEILING function to round up to a multiple.
