Excel Function FLOOR.MATH

FLOOR.MATH(number [,significance] [,mode])

Returns the number rounded down to the nearest integer or significant figure (including negative).

number	The number to be rounded down.
significance	(Optional) The multiple you want the number rounded to.
mode	(Optional) Whether to round negative numbers up or down: False = Negative numbers are rounded up towards zero (default) True = Negative numbers are rounded down away from zero

Remarks

* Added in Excel 2013.
* This function replaces the FLOOR.PRECISE function.
* This function replaces the FLOOR function.
* If "significance" is left blank, then 1 is used.
* If "mode" is left blank, then False is used.
* The "mode" argument only affects negative numbers.
* The "mode" argument can also take numerical values. 0 is equivalent to False. Any other number is equivalent to True.
* If "number" is an exact multiple of "significance", there will be no rounding.
* If "number" is divided by a significance of 2 or greater, results in a remainder, the result is rounded down.
* Positive decimal numbers are rounded down to the nearest integer.
* Negative decimal numbers are rounded down to the nearest integer.
* You can use the CEILING.MATH function to round up to the nearest integer or significant figure.
* You can use the MROUND function to round to a desired multiple.
* You can use the ROUND function to round to a specified number of digits.
* You can use the TRUNC function to return the number with any decimal places removed.
* You can use the INT function to return a number rounded down to the nearest integer.
* For the Microsoft documentation refer to support.office.com

	A
1	=FLOOR.MATH(1.1,1) = 1
2	=FLOOR.MATH(1.5,1) = 1
3	=FLOOR.MATH(1.9,1) = 1
4	=FLOOR.MATH(-1.1,-1) = -2
5	=FLOOR.MATH(-1.5,-1) = -2
6	=FLOOR.MATH(-1.9,-1) = -2
7	=FLOOR.MATH(2.5,2) = 2
8	=FLOOR.MATH(-2.5,-2) = -4
9	=FLOOR.MATH(8,1.5) = 8
10	=FLOOR.MATH(8.26,0.05) = 8.3
11	=FLOOR.MATH(0.234,0.01) = 0.23
12	=FLOOR.MATH(4.2,1) = 4
13	=FLOOR.MATH(4.2,-1) = 4
14	=FLOOR.MATH(4.2,2) = 4
15	=FLOOR.MATH(4.2,-2) = 4
16	=FLOOR.MATH(-4.2,1) = -5
17	=FLOOR.MATH(-4.2,-1) = -5
18	=FLOOR.MATH(-4.2,2) = -6
19	=FLOOR.MATH(-4.2,-2) = -6
20	=FLOOR.MATH(4,-2) = 4
21	=FLOOR.MATH(-2.5,2) = -4
22	=FLOOR.MATH(-4.2,1,TRUE) = -4
23	=FLOOR.MATH(-4.2,-1,TRUE) = -4
24	=FLOOR.MATH(-4.2,2,TRUE) = -4
25	=FLOOR.MATH(-4.2,-2,TRUE) = -4
26	=FLOOR.MATH(NOW(),"0:20") = 9:20:00 AM

Rounding down to the nearest 20 minutes.