IF function
The IF function is one of the most popular functions in Excel, and it allows you to make logical comparisons between a value and what you expect.
So an IF statement can have two results. The first result is if your comparison is True, the second if your comparison is False.
For example, =IF(C2=”Yes”,1,2) says IF(C2 = Yes, then return a 1, otherwise return a 2).
Syntax
Use the IF function, one of the logical functions, to return one value if a condition is true and another value if it's false.
IF(logical_test, value_if_true, [value_if_false])
For example:

=IF(A2>B2,"Over Budget","OK")

=IF(A2=B2,B4A4,"")
Argument name  Description 

logical_test (required) 
The condition you want to test. 
value_if_true (required) 
The value that you want returned if the result of logical_test is TRUE. 
value_if_false (optional) 
The value that you want returned if the result of logical_test is FALSE. 
Simple IF examples

=IF(C2=”Yes”,1,2)
In the above example, cell D2 says: IF(C2 = Yes, then return a 1, otherwise return a 2)

=IF(C2=1,”Yes”,”No”)
In this example, the formula in cell D2 says: IF(C2 = 1, then return Yes, otherwise return No)As you see, the IF function can be used to evaluate both text and values. It can also be used to evaluate errors. You are not limited to only checking if one thing is equal to another and returning a single result, you can also use mathematical operators and perform additional calculations depending on your criteria. You can also nest multiple IF functions together in order to perform multiple comparisons.

=IF(C2>B2,”Over Budget”,”Within Budget”)
In the above example, the IF function in D2 is saying IF(C2 Is Greater Than B2, then return “Over Budget”, otherwise return “Within Budget”)

=IF(C2>B2,C2B2,0)
In the above illustration, instead of returning a text result, we are going to return a mathematical calculation. So the formula in E2 is saying IF(Actual is Greater than Budgeted, then Subtract the Budgeted amount from the Actual amount, otherwise return nothing).

=IF(E7=”Yes”,F5*0.0825,0)
In this example, the formula in F7 is saying IF(E7 = “Yes”, then calculate the Total Amount in F5 * 8.25%, otherwise no Sales Tax is due so return 0)
Note: If you are going to use text in formulas, you need to wrap the text in quotes (e.g. “Text”). The only exception to that is using TRUE or FALSE, which Excel automatically understands.
Common problems
Problem  What went wrong 

0 (zero) in cell 
There was no argument for either value_if_true or value_if_False arguments. To see the right value returned, add argument text to the two arguments, or add TRUE or FALSE to the argument. 
#NAME? in cell 
This usually means that the formula is misspelled. 
Need more help?
You can always ask an expert in the Excel Tech Community, get support in the Answers community, or suggest a new feature or improvement on Excel User Voice.
See Also
Calculation operators and precedence in Excel
Use nested functions in a formula
Using IF to check if a cell is blank
Using IF to check if a cell is blank
IFS function (Office 365, Excel 2016 and later)
Advanced IF functions  Working with nested formulas and avoiding pitfalls
Training videos: Advanced IF functions
The COUNTIF function will count values based on a single criteria
The COUNTIFS function will count values based on multiple criteria
The SUMIF function will sum values based on a single criteria
The SUMIFS function will sum values based on multiple criteria