How to use the FLOOR.MATH function
What is the FLOOR.MATH function?
The FLOOR.MATH function rounds a number down to the nearest integer or to the nearest multiple of significance.
Table of Contents
1. Introduction
What is a multiple?
In mathematics a multiple is a number that can be divided evenly by another number with no remainder. For a number to be a multiple it must be divisible by x with 0 remainder.
For a number x, multiples of x are numbers like 2x, 3x, 4x and so on. For example, 20 is a multiple of 4 since 20/ 4 = 5 with no remainder.
How to round numbers?
Rounding is a method to simplify a number by reducing its digits while keeping its approximate value close to the original value.
There are a few common ways to round:
- Round to a set number of decimal places, rounding 2.13579 to 2 decimal places gives 2.14.
- Round up or down to the nearest integer, rounding up 2.3 gives 3. Rounding down 2.3 gives 2.
- Round to a set increment, rounding to the nearest 10 rounds 17 to 20.
- Round to significant figures, rounding 2.333 to 3 significant figures gives 2.33.
When rounding, look at the first digit after where you want to round. If it's 5 or more, round up. If less than 5, round down. Rounding makes numbers cleaner and easier to work with in many everyday situations, however, they may also cause rounding errors like rounded values can compound errors. Rounding measurements and constants may reduces precision. It is better to round numbers after performing calculations than before.
What is a decimal place?
A decimal place refers to each position held by a digit in a number. The first decimal place is the tenths place (1/10), the second is the hundreds place (1/100) and so on.
What is a comma?
Commas are frequently used in large numbers to help read and interpret the values easier. Commas separate thousands place values in large numbers. For example:
- 10,000 - ten thousand
- 100,000 - one hundred thousand
- 1,000,000 - one million
The comma creates groups of three digits, making it easier to count the zeroes and understand the scale.
In decimal numbers with both whole and fractional parts, commas separate the whole number groups of three digits. For example:
- 3,421.256
- 102,734,221.985
What is an integer?
An integer is a whole number that can be positive, negative, or zero, but not a fraction or decimal.
What other Excel functions round numbers?
| ROUND | Rounds a number to a specified number of digits |
| ROUNDUP | Rounds a number up, away from zero |
| ROUNDDOWN | Rounds a number down, towards zero |
| MROUND | Rounds a number to the nearest multiple of a specified value |
| CEILING | Rounds a number up to its nearest multiple. |
| ODD | Returns number rounded up to the nearest odd integer. |
| EVEN | Rounds a number up to the nearest even whole number. |
| FIXED | Rounds a number to the specified number of decimals, lets you ignore comma separators. |
| FLOOR.MATH | Rounds a number down to the nearest integer or to the nearest multiple of significance. |
| FLOOR.PRECISE | Rounds a number down to the nearest integer or to the nearest multiple of significance. |
2. Syntax
FLOOR.MATH(number, [significance], [mode])
| number | Required. The number to be rounded down. |
| [significance] | Optional. The multiple to which you want to round. |
| [mode] | Optional. The direction (toward or away from 0) to round negative numbers. |
3. Example 1
This example shows how to use the FLOOR.MATH function with different arguments. The image shows the number to round down to its nearest multiple of significance in column B, the significance argument in column C and the mode in column D. The result is shown in column F.
The first number in cell B3 is 34.721. The arguments are:
- number - B3 (a cell reference to the value we want to round)
- [significance] - C3 (a cell reference to the multiple of significance)
- mode: not specified (The direction toward or away from 0 to round negative numbers)
Formula in cell F3:
Cell F3 returns 34 based on 34.721 and 1 as the multiple of significance. 34 is the nearest multiple of significance if rounded down.
The second number is in cell B4 which is -15631.053. The arguments are:
- number - B4 (a cell reference to the value we want to round)
- [significance] - C4 (a cell reference to the multiple of significance)
- mode: not specified (The direction toward or away from 0 to round negative numbers)
Formula in cell F3:
Cell F3 returns -15632 based on input number -15631.053 and the multiple of significance is 2. -15632 is the nearest multiple of significance if rounded down.
The third number is in cell B5 which is also -15631.053. The arguments are:
- number - B5 (a cell reference to the value we want to round)
- [significance] - C5 (a cell reference to the multiple of significance)
- mode: -1 (The direction toward or away from 0 to round negative numbers)
Formula in cell F3:
Cell F3 returns -15630 based on input number -15631.053, the multiple of significance is 2, and the mode argument is -1 meaning it rounds up if the input value is a negative value. -15630 is the nearest multiple of significance if rounded up.
4. Example 2
A rectangular shape has an area equal to the square root of 92 square units. If the length of this rectangle is 4 units, what is its width? Round the number down to an multiple of significance of 0.2 using the MATH.FLOOR function.
Lets begin calculating the width of the rectangular shape. Area is the size of the surface enclosed by the rectangle expressed in square units like square meters, square feet, etc. Width is the measure of one of the shorter sides of the rectangle perpendicular to the length.
The units used for length and width must be the same and the area will be expressed in square units of those same units.
Area = length * width
Area = square root of 92
height = 4
width = area / length
width = √92 / 4
FLOOR.MATH arguments:
number = 92^0.5 / 4
significance = 0.2
Formula in cell C21:
√92 / 4 = 2.39791576165636 and the FLOOR.MATH function converts it to 2.2 units which represents the width of the rectangular shape.
5. Function not working
The FLOOR.MATH function returns a
- #VALUE! error if one of the arguments is non-numeric
- #NAME! error if the function is misspelled.
- Propagates the error value if the source value is an error value. If a cell contains an error value, such as #N/A, #VALUE!, #REF!, #DIV/0!, #NUM!, #NAME?, or #NULL!, and that cell is used as an argument in a function, the function will typically return the same error value.
5.1 Troubleshooting the error value
When you encounter an error value in a cell a warning symbol appears, displayed in the image above. Press with mouse on it to see a pop-up menu that lets you get more information about the error.
- The first line describes the error if you press with left mouse button on it.
- The second line opens a pane that explains the error in greater detail.
- The third line takes you to the "Evaluate Formula" tool, a dialog box appears allowing you to examine the formula in greater detail.
- This line lets you ignore the error value meaning the warning icon disappears, however, the error is still in the cell.
- The fifth line lets you edit the formula in the Formula bar.
- The sixth line opens the Excel settings so you can adjust the Error Checking Options.
Here are a few of the most common Excel errors you may encounter.
#NULL error - This error occurs most often if you by mistake use a space character in a formula where it shouldn't be. Excel interprets a space character as an intersection operator. If the ranges don't intersect an #NULL error is returned. The #NULL! error occurs when a formula attempts to calculate the intersection of two ranges that do not actually intersect. This can happen when the wrong range operator is used in the formula, or when the intersection operator (represented by a space character) is used between two ranges that do not overlap. To fix this error double check that the ranges referenced in the formula that use the intersection operator actually have cells in common.
#SPILL error - The #SPILL! error occurs only in version Excel 365 and is caused by a dynamic array being to large, meaning there are cells below and/or to the right that are not empty. This prevents the dynamic array formula expanding into new empty cells.
#DIV/0 error - This error happens if you try to divide a number by 0 (zero) or a value that equates to zero which is not possible mathematically.
#VALUE error - The #VALUE error occurs when a formula has a value that is of the wrong data type. Such as text where a number is expected or when dates are evaluated as text.
#REF error - The #REF error happens when a cell reference is invalid. This can happen if a cell is deleted that is referenced by a formula.
#NAME error - The #NAME error happens if you misspelled a function or a named range.
#NUM error - The #NUM error shows up when you try to use invalid numeric values in formulas, like square root of a negative number.
#N/A error - The #N/A error happens when a value is not available for a formula or found in a given cell range, for example in the VLOOKUP or MATCH functions.
#GETTING_DATA error - The #GETTING_DATA error shows while external sources are loading, this can indicate a delay in fetching the data or that the external source is unavailable right now.
5.2 The formula returns an unexpected value
To understand why a formula returns an unexpected value we need to examine the calculations steps in detail. Luckily, Excel has a tool that is really handy in these situations. Here is how to troubleshoot a formula:
- Select the cell containing the formula you want to examine in detail.
- Go to tab “Formulas” on the ribbon.
- Press with left mouse button on "Evaluate Formula" button. A dialog box appears.
The formula appears in a white field inside the dialog box. Underlined expressions are calculations being processed in the next step. The italicized expression is the most recent result. The buttons at the bottom of the dialog box allows you to evaluate the formula in smaller calculations which you control. - Press with left mouse button on the "Evaluate" button located at the bottom of the dialog box to process the underlined expression.
- Repeat pressing the "Evaluate" button until you have seen all calculations step by step. This allows you to examine the formula in greater detail and hopefully find the culprit.
- Press "Close" button to dismiss the dialog box.
There is also another way to debug formulas using the function key F9. F9 is especially useful if you have a feeling that a specific part of the formula is the issue, this makes it faster than the "Evaluate Formula" tool since you don't need to go through all calculations to find the issue..
- Enter Edit mode: Double-press with left mouse button on the cell or press F2 to enter Edit mode for the formula.
- Select part of the formula: Highlight the specific part of the formula you want to evaluate. You can select and evaluate any part of the formula that could work as a standalone formula.
- Press F9: This will calculate and display the result of just that selected portion.
- Evaluate step-by-step: You can select and evaluate different parts of the formula to see intermediate results.
- Check for errors: This allows you to pinpoint which part of a complex formula may be causing an error.
The image above shows cell reference B3:B10 converted to hard-coded value using the F9 key. The FLOOR.MATH function requires numerical values which is not the case in this example. We have found what is wrong with the formula.
Tips!
- View actual values: Selecting a cell reference and pressing F9 will show the actual values in those cells.
- Exit safely: Press Esc to exit Edit mode without changing the formula. Don't press Enter, as that would replace the formula part with the calculated value.
- Full recalculation: Pressing F9 outside of Edit mode will recalculate all formulas in the workbook.
Remember to be careful not to accidentally overwrite parts of your formula when using F9. Always exit with Esc rather than Enter to preserve the original formula. However, if you make a mistake overwriting the formula it is not the end of the world. You can “undo” the action by pressing keyboard shortcut keys CTRL + z or pressing the “Undo” button
5.3 Other errors
Floating-point arithmetic may give inaccurate results in Excel - Article
Floating-point errors are usually very small, often beyond the 15th decimal place, and in most cases don't affect calculations significantly.
Functions in 'Math and trigonometry' category
The FLOOR.MATH function function is one of 62 functions in the 'Math and trigonometry' category.
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