FLOOR.MATH Function in Excel: Round Down to a Multiple

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MathLevel: IntermediateAvailable in: Excel 2013+

In this article

1. Syntax
2. Examples
3. Example 1
4. Example 2
5. FLOOR.MATH in practice
6. Where you will use it
7. Worked example
8. Mistakes people make
9. Related functions
10. Continue learning

FLOOR.MATH rounds down to the nearest multiple — slabs, time buckets and whole units.

Syntax

=FLOOR.MATH(number, [significance])

Argument	What it means
significance	The multiple.

Examples

Example 1

=FLOOR.MATH(A2, "0:30")

Group times into 30-minute buckets.

Example 2

=FLOOR.MATH(B2, 1000)

Income to the lower thousand.

FLOOR.MATH in practice

Where you will use it

• Round down with negatives handled predictably
• Full boxes from stock
• Slab calculations

Worked example

Value	Step	Formula	Result
-7.3	1	=FLOOR.MATH(A2,B2)	-8
47	12	=FLOOR.MATH(A3,B3)	36
12.9	0.5	=FLOOR.MATH(A4,B4)	12.5

Results calculated in Excel.

Mistakes people make

Mistake	What to do instead
Negatives go away from zero	-7.3 becomes -8; set mode to 1 to round toward zero
Missing step	Default step is 1

Related functions

CEILING.MATH · MROUND

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📎 Practice files for this article

• 📗
  Practice workbook: Math & rounding24 tasks on realistic sales data — type your formula, the Check column turns green when it is right. Answers sheet included.
  ⬇ XLSX · 35 KB

Free to use for learning. Files with macros (.bas) are plain text — import them with Alt+F11 → File → Import File, and always test on a copy.