Using If,Then function in Excel - excel

Question

I have a retail store that sells items on consignment for a fee that varies based on Selling Price.
So my question is how do I write a formula that checks the selling price and then charges the correct consignment fee to calculate the net based on the following schedule:
When selling price is over $400 then charge = 20%
When Selling price is $100 to $400 then charge = 30%
When Selling price is under $100 then charge = 40%

Answer 1

BLUF: use nested IF statements (an IF inside an IF) --
Example:
=IF(A2>=400, (A2*0.2), (IF(400 > A2 >= 100, (A2 *0.3), (A2*0.4))))
Or use the below if you suspect someone will foolishly enter a negative number or something nonsensical:
=IF(A2>=400, (A2*0.2), (IF(400 > A2 >= 100, (A2 *0.3), (IF(A2 < 100, (A2*0.4), (0))))))
That may look complex, but let's break it down from the beginning.
The basic formula for the IF statement:
=IF(testCondition, (resultIfTrue), (resultIfFalse))
One IF statement will only allow you to do two of your 3 conditions:
=IF(A1 > 400, (A1 * .20), (A1 * .30))
The above basically says that if the number in cell A1 is greater than 400, then the value in your current cell (e.g. B2) is A1 * 20%. But if the number in A1 is NOT greater than 400, the value in your cell will be A1 * 30%.
But how do we calculate the range you were asking (i.e. 100 - 400) and how do we add in a third possibility (i.e. the possibility that the number is less than 100)?
The answer is to use a nested IF. You can tell the cell what it's value should be if the condition is true, but you can test another condition if the answer is false (i.e. the next IF statement stands in the place of resultIfFalse.
=IF(testCondition, (resultIfTrue), (IF(testCondition, (resultIfTrue), (resultIfFalse))))
The above can handle 3 different scenarios. Out of the IFs above, you could also replace the second IFs resultIfFalse with yet another IF statement, and so on. You can nest up to 64 IF statements.
Extra Resources:
http://fiveminutelessons.com/learn-microsoft-excel/using-multiple-if-statements-excel
http://spreadsheets.about.com/od/tipsandfaqs/qt/nested_if.htm

Answer 2

Nested IF functions are not user friendly and require hardcoding your variables (percentages). My suggestion would always be to have a small table of values elsewhere: eg. put the following in A1:B3
0 0.4
100 0.3
401 0.2
Assuming your data is in D1 you can use the following formula in E1 and drag down if necessary
=INDEX($B$1:$B$3,MATCH($D1,$A$1:$A$3,1))
This way you can change your boundaries/ add more conditions easily without more nested IF statements

Answer 3

Try using this instead:
=IF(B1<100,B1*40%,IF((B1>=100)*AND(B1<=400),B1*30%,IF(B1>100,B1*20%,"Invalid Price"))
This formula contains nested-ifs and a logical AND condition which will give the result.