How to use the ISLOGICAL function
What is the ISLOGICAL function?
The ISLOGICAL function returns TRUE if value is boolean.
Table of Contents
1. Introduction
What is a Boolean value?
A Boolean value in Excel is a value that can only be TRUE or FALSE. It represents binary logic and is the result of a logical expression using logical operators or a result of a few Excel functions that I'll discuss below.
Mastering Boolean logic and logical expressions is key to manipulating data and controlling workflow in Excel.
What is binary logic?
Binary logic refers to values having one of two states, TRUE or FALSE. This allows Boolean algebra in Excel using logical operators.
What is a logical expression?
A logical expression is a statement that evaluates to TRUE or FALSE. For example:
=A1<4
These expressions use comparison operators to evaluate a condition and produce a Boolean result.
What are the comparison operators?
= - equal sign
< - less than sign
> - greater than sign
These operators let you build more operators like this:
<> - not equal to
<= - less than or equal to
>= - greater than or equal to
These comparison operators let you create logical expressions like: A2<>5 meaning if the value in cell A2 is not equal to 5, the result is either TRUE or FALSE.
What are the logical operators?
The main logical operators in Excel are:
- AND - Returns TRUE if all conditions are true
- OR - Returns TRUE if any condition is true
- NOT - Negates a logical expression
- XOR - Returns TRUE if only one condition is true
Other IS functions
| Excel Function | Description |
|---|---|
| ISBLANK(value) | Returns TRUE if the value is empty, FALSE otherwise |
| ISERR(value) | Returns TRUE if the value is any error value except #N/A, FALSE otherwise |
| ISERROR(value) | Returns TRUE if the value is any error value, FALSE otherwise |
| ISEVEN(value) | Returns TRUE if the value is an even number, FALSE for odd numbers |
| ISFORMULA(reference) | Returns TRUE if the cell contains a formula, FALSE otherwise |
| ISLOGICAL(value) | Returns TRUE if the value is a logical value (TRUE/FALSE), FALSE otherwise |
| ISNA(value) | Returns TRUE if the value is the #N/A error, FALSE otherwise |
| ISNONTEXT(value) | Returns TRUE if the value is not text, FALSE if it is text |
| ISNUMBER(value) | Returns TRUE if the value is a number, FALSE otherwise |
| ISODD(value) | Returns TRUE if the value is an odd number, FALSE for even numbers |
2. Syntax
ISLOGICAL(value)
| value | Required. The value you want to check for a boolean value. |
What is a cell reference?
A cell reference lets you "fetch" and use values in other cells in a formula.
There are two types of cell references:
- A1-style reference
- R1C1 reference
The A1-style reference is the default style in Excel, it names columns by letters from A to Z. After Z it starts over with AA, AB, and so on until XFD. Rows are numbered from 1 to 1048576, older Excel versions use less row numbers.
The R1C1-style uses row number and column number like: R1C1, R2C5 and R10C15. Rows are labeled R1, R2, R3 and so on, columns are labeled C1, C2, C3 etc.
The A1-style reference notation is the most common one, here are some examples:
A1 - single cell reference on the same worksheet
A1:D5 - reference to a cell range on the same worksheet
Budget!Z3 - a single cell reference to worksheet Budget
'Budget 2050'!A3 - a single cell reference to a worksheet containing a space character
There are two types of cell references:
- Relative cell references
- Absolute cell references
The examples above are all relative cell references, they change accordingly if a cell is copied and pasted to another cell which absolute cell references do not.
The $ dollar character lets you an absolute cell reference meaning you can lock a cell reference horizontally, vertically or both. Here is one example:
A$1 has a relative column reference but an absolute row reference, this means that the column letter may change if the cell is copied and pasted to cells in another column than A.
3. Example
The image shows the results of using the ISLOGICAL function in Excel for different input values. The ISLOGICAL function checks whether a given value is a logical value (TRUE or FALSE) and returns TRUE if it is, and FALSE if it's not.
Formula in cell C3:
Cell B3 contains text value "A" which is not a logical value. The formula in cell C3 returns FALSE.
Formula in cell C4:
Cell B4 contains numerical value 1 which is not a logical value.The formula in cell C4 returns FALSE.
Formula in cell C5:
Cell B5 contains boolean value TRUE which is a logical value.The formula in cell C5 returns TRUE.
Formula in cell C6:
Cell B6 contains value #DIV/0! which is an error value and not a boolean value. The formula in cell C6 returns FALSE.
Formula in cell C7:
Cell B7 contains value #N/A! which is an error value and not a boolean value. The formula in cell C7 returns FALSE.
Formula in cell C8:
Cell B8 contains value #VALUE! which is an error value and not a boolean value. The formula in cell C8 returns FALSE.
Formula in cell C9:
Cell B9 contains value #NAME! which is an error value and not a boolean value. The formula in cell C9 returns FALSE.
Formula in cell C10:
Cell B10 contains value FALSE which is a boolean value. The formula in cell C10 returns TRUE.
The ISLOGICAL function only returns TRUE for the boolean values TRUE and FALSE. For all other types of input (text, numbers, errors), it returns FALSE. The ISLOGICAL function is very useful to identify error values in arrays. Most Excel functions return the same error value, however, this function returns FALSE if it encounters an error.
4. Function not working
The ISLOGICAL function returns
- #NAME? error if you misspell the function name.
- #SPILL! error occurs in Excel 365 when a dynamic array formula returns an array that cannot fit into the available cells.
The ISLOGICAL function does not propagate errors, meaning that if the input contains an error (e.g., #VALUE!, #REF!), the ISLOGICAL function will return FALSE rather than displaying the error itself. This allows you to test whether a value is a logical TRUE or FALSE without interruption from errors in the data.
Note that Excel interprets a number not equal to 0 (zero) as TRUE and 0 (zero) as FALSE, for example, in a IF function. However, the ISLOGICAL function does not.
4.1 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.
4.2 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 B10 converted to hard-coded value using the F9 key. The ISLOGICAL function requires you to spell the function name correctly 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
4.3 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 'Information' category
The ISLOGICAL function function is one of 19 functions in the 'Information' category.
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