IFERROR & ROUND
Handle known exceptions and choose a deliberate precision policy.
By the end, you’ll be able to:
- Use a meaningful fallback for an error
- Distinguish rounded values from rounded display
- Preserve valid zero results and diagnose hidden problems
Inspect the original calculation first
Unit cost equals total Cost divided by Units. For item A, 100 ÷ 3 gives 33.3333…; item B has zero units and produces #DIV/0!. Item C has zero cost and five units, giving a valid zero.
A fallback should reflect the business meaning. “Check units” tells a reader that a unit-cost result is unavailable. Replacing every error with zero can make a broken input look like a free unit.
| A | B | C | |
|---|---|---|---|
| 1 | Item | Cost | Units |
| 2 | A | 100 | 3 |
| 3 | B | 45 | 0 |
| 4 | C | 0 | 5 |
Handle errors with a deliberate alternative
=IFERROR(value, value_if_error)value is the expression to calculate. value_if_error is the result to use if that expression produces an Excel error. Valid zero and FALSE results are not errors.
=IFERROR(B2/C2,"Check units") returns 33.3333… for item A and Check units for a zero-unit case. IFERROR catches multiple kinds of errors, not just division by zero. If your only intended exception is a zero denominator, an explicit IF(C2=0,...) guard makes that policy narrower.
Round the value when the calculation requires it
=ROUND(number, num_digits)number is the value or calculation. num_digits gives decimal places: 2 for hundredths, 0 for whole numbers, and negative values for positions to the left of the decimal point.
=ROUND(B2/C2,2) returns 33.33. =ROUND(1234,-2) returns 1200. Excel rounds a halfway value away from zero; consider the precision policy and floating-point inputs when checking sensitive calculations.
Formatting and rounding are different actions
Displaying 100/3 with two decimals shows 33.33 while the underlying value remains approximately 33.3333. ROUND changes the calculated result to 33.33. Multiplying by 3 then gives 99.99 rather than 100.
Choose whether policy requires rounding each line before summing, or summing full-precision values and rounding once. Those methods can disagree. Document the rule rather than repeatedly adding ROUND until a total matches an expectation.
Combine handling with a precision rule
=IFERROR(ROUND(B2/C2,2),"Check units") returns a two-decimal calculated unit cost when division succeeds and a message when it fails. Test ordinary data, zero units and valid zero cost.
Review a sample of fallback rows so a broken reference or text input is not hidden by the friendly message. IFERROR and ROUND work in current web Excel and established desktop editions. The checker supports the lesson’s numeric cases; it is not a substitute for checking a workbook’s input quality.
Give it a try.
Work through each exercise, check your answer and use a hint whenever you need one. Formula tasks check changed inputs, including boundary cases.
0 of 4 exercises complete
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Take this with you
Use an informative error fallback, preserve valid zero and distinguish display precision from a deliberate rounding policy.
Practice in Excel
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Original lesson content. Technical behavior checked against Microsoft documentation. Reviewed 2026-10-16.