← ACARA Digital Technologies Years 9–10

The IFERROR function

Runs a formula and shows your chosen value, like 0 or "Not found", if it gives an error. Use it carefully, because it can also hide real mistakes.

Part of: ACARA Digital Technologies Years 9–10 — Analysing and Visualising Data — Module 24

Understanding The IFERROR function in ACARA Digital Technologies Years 9–10

What it does: The first argument is the formula that is tested and the second is the replacement value shown when an error happens. Empty quotation marks make IFERROR show nothing when B2/C2 gives an error, so the sheet looks tidy. Wrap the whole XLOOKUP inside IFERROR, then add the text to show as the second argument. Text must be in quotes. 10/2 works fine and gives 5, so IFERROR does not use the backup value of 0. IFERROR can hide real mistakes. If a formula is broken, fix the cause rather than covering it up with a 0 or a message. Fix the range or the data first. Only use IFERROR for errors you expect, like dividing by zero or a missing lookup match.

Common mistakes: IFERROR needs two arguments: the formula and the value to show if it fails. The value_if_error is missing. It should be =IFERROR(B2/C2,0). The closing bracket is missing, so the function is not finished. It should be D4: =IFERROR(B4/C4,0).

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This module's key terms are also in a printable crossword (Modules 378–412) and word search (Modules 333–412).

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Learning
Duo
Which formula shows 0 instead of an error when C2 is 0?
=IFERROR(B2/C2)=IFERROR(B2/C2,0)
Matches
=IFERROR(B2/C2)
↓
The value_if_error argument is missing. IFERROR needs two arguments: the formula and what to show if it fails.
Applying
Meanings
Term
=IFERROR(value, value_if_error)
Meaning
Runs a formula and shows your chosen value, like 0 or "Not found", if it gives an error. Use it carefully, because it can also hide real mistakes.
Practice
=IFERROR(B2/D2,"No rain")
Testing
Gaps
=(B2/C2,0)
Check Answer
Spots
1=IFERROR(B2/C2,0)
2=IFERROR(B2/C2)

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Quick Questions

1. Which formula shows 0 instead of an error when C2 is 0?
A. =IFERROR(B2/C2)
B. =IFERROR(B2/C2,0) ✓
IFERROR needs two parts: the formula to try and the value to show if it fails. =IFERROR(B2/C2,0) shows 0 when dividing by zero.
2. True or false: IFERROR shows your chosen value only when the formula gives an error.
A. False
B. True ✓
If the formula works, you see its normal result. The chosen value only appears when there is an error like #DIV/0! or #N/A.
3. Which formula shows "Not found" when a name is missing from a lookup?
A. =IFERROR(XLOOKUP(A2,F:F,G:G),"Not found") ✓
B. =XLOOKUP(A2,F:F,G:G,"Not found",IFERROR)
Wrap the whole XLOOKUP inside IFERROR, then add the text to show as the second argument. Text must be in quotes.
4. What does =IFERROR(10/2,0) show?
A. 5 ✓
B. 0
10/2 works fine and gives 5, so IFERROR does not use the backup value of 0.
5. A formula shows #REF! because a column was deleted by mistake. Which is the better fix?
A. Find out why the error happens and repair the formula ✓
B. Wrap it in IFERROR so the error disappears
IFERROR can hide real mistakes. If a formula is broken, fix the cause rather than covering it up with a 0 or a message.

Match the Pairs

=IFERROR(B2/C2,0) → Divides B2 by C2 and shows 0 if the division gives an error, such as dividing by zero
=IFERROR(XLOOKUP(A2,F:F,G:G),"Not found") → Looks up A2 and shows the words Not found if no match exists
IFERROR takes the formula to try first, then the value to show if that formula gives an error → =IFERROR(value, value_if_error)
Show a blank cell instead of an error when a percentage formula fails → =IFERROR(B2/C2,"")
=IFERROR(B2/C2) → The value_if_error argument is missing. IFERROR needs two arguments: the formula and what to show if it fails.
=IFERROR(SUM(B2:B9),0) to hide a wrong cell range that points at the wrong column → IFERROR hides real mistakes. Wrapping a formula to cover up a wrong range means the problem is never found or fixed.

Key Term

=IFERROR(value, value_if_error)
Runs a formula and shows your chosen value, like 0 or "Not found", if it gives an error. Use it carefully, because it can also hide real mistakes.

Fill in the Blanks

1. =IFERROR(B2/C2,0)
Hint: Type the function name that swaps an error for a value you choose.
2. =IFERROR(B2/C2,0)
Hint: Type the number that will show in the cell when the division fails.
3. =IFERROR(XLOOKUP(E2,A2:A9,B2:B9),"Not found")
Hint: Type the lookup function that IFERROR is wrapped around.
4. =IFERROR(D2/E2,0)
Hint: Type the arithmetic operator that divides D2 by E2, which could cause a #DIV/0! error.
5. =IFERROR(B2/C2,0)
Hint: Type the calculation that might fail. It is the first argument and only this part should be checked.

Spot the Error

Question 1
A =IFERROR(B2/C2,0)
B =IFERROR(B2/C2)
C =IFERROR(B4/C4,0)
Line B — IFERROR needs two arguments: the formula and the value to show if it fails. The value_if_error is missing. It should be =IFERROR(B2/C2,0).
Question 2
A Price per item in column D
B D2: =IFERROR(B2/C2,0)
C D3: =IFERROR(B3/C3,0)
D D4: =IFERROR(B4/C4,0
Line D — The closing bracket is missing, so the function is not finished. It should be D4: =IFERROR(B4/C4,0).
Question 3
A D2: =IFERROR(C2,Not found)
B D3: =IFERROR(C3,"Not found")
C D4: =IFERROR(C4,"Not found")
Line A — Text in a formula must be inside double quotes. Without them Not found is read as a name and causes an error. It should be =IFERROR(C2,"Not found").
Question 4
A Average mark, no errors shown:
B =IFERROR(0,AVERAGE(B2:B9))
C Empty range gives 0, no error
Line B — The arguments are the wrong way round. The formula to test comes first and the replacement value comes second. It should be =IFERROR(AVERAGE(B2:B9),0).
Question 5
A Total in B2, students in C2
B D2: IFERROR(B2/C2,0)
C D2 shows 0 if C2 is empty
Line B — Every formula must start with =. Without it the cell shows plain text instead of calculating. It should be D2: =IFERROR(B2/C2,0).

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