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In this article
DEC2BIN converts a number to binary text. Good for teaching, flags and subnet masks, but it only handles −512 to 511.
Syntax
=DEC2BIN(number, [places])| Argument | What it means |
|---|---|
places |
Pad with leading zeros. |
Examples
Example 1
=DEC2BIN(13, 8)Returns 00001101.
Common errors and fixes
| You see | Why, and the fix |
|---|---|
#NUM! |
Number outside −512…511. Use BASE(n, 2) for bigger values. |
DEC2BIN in practice
Where you will use it
- Show numbers as binary for bit flags
- Teaching number systems
- Check subnet masks
Worked example
| Number | Formula | Result |
|---|---|---|
| 5 | =DEC2BIN(A2,8) | 00000101 |
| 10 | =DEC2BIN(A3,8) | 00001010 |
| 255 | =DEC2BIN(A4,8) | 11111111 |
Results calculated in Excel.
Mistakes people make
| Mistake | What to do instead |
|---|---|
| Numbers above 511 | DEC2BIN handles -512 to 511; use BASE for bigger numbers |
| Missing padding | The second argument pads with zeros |
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📎 Practice files for this article
- 📗Practice workbook: Engineering & conversion15 tasks on realistic sales data — type your formula, the Check column turns green when it is right. Answers sheet included.⬇ XLSX · 34 KB
Free to use for learning. Files with macros (.bas) are plain text — import them with Alt+F11 → File → Import File, and always test on a copy.
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