COMBIN Function in ONLYOFFICE Spreadsheet Editor: Choose Without Order

Choose COMBIN when choosing A+B and B+A represents the same selected set, e.g. selecting two committee members from five, or choosing a three-item sample from eight without considering order. Do not use it to count PINs, ranks, seating orders or sequences: PERMUT applies to order-sensitive selections.

For integers n and k with 0 ≤ k ≤ n, the mathematical formula is n choose k = n! / (k! × (n−k)!). Important vendor-specific wrinkle: the current ONLYOFFICE COMBIN page explicitly describes number_chosen as at least zero but less than number. That wording is stricter than the usual mathematical identity n choose n = 1. This article uses k<n in the main examples and does not assert what ONLYOFFICE does for k=n until tested natively.

=COMBIN(number, number_chosen)

No arguments are marked optional and no defaults are documented. Exact handling of fractions, negative inputs, text, a chosen count equal to the available count, and floating-point overflows is not specified by the short official page, and was not tested in ONLYOFFICE for this guide. This guide limits its independently computed examples to whole numbers with 0 ≤ k < n. Official claim source (checked 2026-10-13 UTC).

1. On a new scratch sheet type Available n in A1, Chosen k in B1, COMBIN formula in C1, and Expected combinations in D1.
2. Type each pair of A/B values exactly as shown below into rows 2 through 7. These are counts of distinct items, not percentages or percentages formatted as decimals.
3. In C2 enter =COMBIN(A2,B2), then fill through C7; if autofill isn’t available, type each formula exactly as given.
4. Independently calculate the expected D-column values or copy the numbers below as comparison values only. Once you run ONLYOFFICE, put its observed result in C and document whether it matches D.

Manual proof for row 2: 5!/(2!×3!) = (5×4)/(2×1) = 10. Row 3: 8!/(3!×5!)=(8×7×6)/(3×2×1)=56. Row 6: 10!/(4!×6!)=210. The calculations were validated using Python math.comb and arithmetic, not an ONLYOFFICE runtime.

A bag contains 5 blue and 7 red individually distinguishable balls. Five are selected uniformly without replacement; order of the draw does not matter. What is the probability of exactly two blue and three red?

• The favorable unordered selections: choose 2 of 5 blue and 3 of 7 red, giving COMBIN(5,2) × COMBIN(7,3) = 10 × 35 = 350.
• All unordered five-ball selections: COMBIN(12,5)=792.
• Therefore the mathematical probability is 350/792 = 175/396 ≈ 0.4419191919 (44.1919%).

In a scratch editor, the corresponding formula is:

=COMBIN(5,2)*COMBIN(7,3)/COMBIN(12,5)

This is an independently calculated expected numerical result, not a native ONLYOFFICE outcome. Be precise about what is equally likely: the derivation assumes all 5-item subsets of 12 distinct balls are equally likely. If sampling with replacement, the denominator changes and COMBIN alone is not the entire model.

For integer n=8, k=3, these formulas have different mathematical meanings:

The combinatorial relationship PERMUT(8,3) = COMBIN(8,3) × FACT(3) gives 336=56×6. Official PERMUT and official FACT references establish function identities; the exact numbers are independently calculated. These are separate canonical functions, not alias spellings.

• Accidentally counting order: seating 3 different people in 8 numbered chairs is a permutation problem, not simply a 3-person committee.
• Using duplicate items without a defined sampling model: decide whether physical items are distinct and whether replacement is allowed; the formula’s combinatorial count assumes n distinguishable items selected without replacement.
• Equal chosen and available: nCn = 1 mathematically; however ONLYOFFICE’s currently published wording states number_chosen < number. Native outcome for =COMBIN(5,5) is PENDING VERIFICATION, not asserted here as 1 or an error.
• Negative, fractional, text, omitted arguments: exact native input coercion and specific error strings are not provided by the function article. Test them in the selected product and version before making a software-specific claim.
• Displayed rounded output: for large inputs a combinatorial count can be so large that precise integer representation isn’t guaranteed. Use a separately calculated exact-integer reference where exactness matters.

PERMUT counts ordered selections without replacement; COMBINA counts unordered choices where repetitions are allowed; FACT helps derive the mathematical identity. These links lead to the official vendor references. The differences in meanings warrant distinct guides rather than alias redirects.

The first and second argument positions, the numeric >=0 restrictions, and the vendor’s < number wording are directly from the ONLYOFFICE COMBIN function page (accessed 2026-10-13 UTC). Mathematical counting identities and each answer in the examples are independent computations. Native QA needs to check: COMBIN(5,5), COMBIN(0,0), fractional n/k, negative k, text inputs, and large counts, recording editor version and exact outcomes. The vendor page does not establish first-supported Desktop/web release.

ONLYOFFICE’s official inserting-functions instructions say to select a cell, type =, enter a recognized function and comma-separated arguments in parentheses, then press Enter; alternatively open the Formula tab, choose Function, search for the name, and fill the argument dialog. The formulas above are written with English function names and comma separators following the published help examples. If your workbook uses a different Formula Language, confirm the localized name in the Function dialog rather than manually translating an English name. This manuscript does not claim that any additional separator style was executed.

Regional settings and formula language

The official Advanced Settings page explains File → Advanced Settings → Regional settings. Formula Language determines translated formula and argument labels. Region influences displayed currency, dates, and times. Separate decimal and thousands separators are customizable. These documented settings are not evidence that a given translated function, localized punctuation style, or imported workbook behaves identically in every deployment. All tables here use ordinary integer inputs so decimal-entry ambiguity is avoided; they have not undergone native non-English testing.

Calculation and validation limits

The listed results are independently calculated mathematical expectations, not observed outputs from a running ONLYOFFICE Desktop, Docs/web, or self-hosted editor. We performed the arithmetic using Python’s integer mathematics; the result checks do not establish formula-parser or spreadsheet-engine support. Enter these test cases on a disposable sheet and compare the editor’s displayed result with the expectation. If different, record the precise ONLYOFFICE version, environment (web/Desktop), formula language, cell type, and exact displayed error before drawing a conclusion about compatibility.

Do not infer first-supported release or universal compatibility. The unversioned help function reference lists this function today, but does not identify the first supported Desktop build or prove behaviour across all self-hosted, Docs/web and embedded editions. The Docs changelog lists Docs 10.0.0, 2026-10-10, while the Desktop Editors changelog is maintained separately; the Docs release alone is not a Desktop version guarantee. No platform-specific native tests or compatibility matrix were executed for this page.

1. Formula displayed as text: ensure the cell contains a formula beginning with =, not a quoted string; check the displayed cell format.
2. Unexpected result: verify the order of arguments, positive/nonnegative integer assumption used in the examples, input cells (not headers), and number formatting. Compare with the arithmetic shown rather than a screenshot.
3. Function not recognized: search in the editor’s Insert Function dialog, check Formula Language, and note the exact desktop/web version. Presence in current web documentation does not guarantee the function was present in older releases.
4. Apparent calculation error: check blank cells, stray text, missing commas, copied relative references and whether the input violates the mathematical domain. The help reference does not provide a comprehensive table of exact error strings for this function; no error code or coercion behaviour is asserted here as an observed ONLYOFFICE result.
5. Large numbers: factorial-style counts can exceed the range where a spreadsheet displays or stores every integer exactly. A rounded display or scientific notation is not proof that the full integer was retained; compare against the independently calculated exact integer where precision matters.

• Official function-entry instructions — how to insert and identify the supported function from the editor UI.
• Official regional and formula-language settings — language, region and separator controls; localized formula execution remains untested.
• ONLYOFFICE Docs release notes and Desktop release notes — separate release tracks; these do not establish this function’s introduction version.

Verification limitations: Native web/Desktop calculation, localized parsing, historical compatibility and undocumented error behavior were not tested. The official function index documents current names, not a release-by-release execution guarantee.