COMBIN function

Returns the number of ways to choose a subset of items from a set when order doesn't matter, useful for sampling strategies and probability calculations.

=COMBIN(number, number_chosen)

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  • Name your columns by letter and by header: "column F (Net Value)" beats "the amount column".
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  • Check the settings above match your spreadsheet: the wrong argument separator is a syntax error on your machine.

Arguments

How COMBIN reads its arguments
numberrequirednumber_chosenrequiredCOMBIN →
ArgumentRequiredDescription
numberRequiredThe total number of items to choose from; must be a non-negative integer (0 or greater).
number_chosenRequiredThe number of items to select from the total; must be a non-negative integer not exceeding number.

Returns

An integer representing the count of unique combinations.

Availability

Excel: All · Google Sheets: Supported

Worked examples

1. Calculate team pairings for joint sales calls

OrderIDRegionRepUnitsUnitPriceOrderDate
101EastAlice5252024-01-15
102WestBob3502024-01-20
103NorthCarol8302024-01-25
104SouthDavid2752024-02-01
105EastEve6402024-02-05
106WestFrank4602024-02-10
107NorthGary7352024-02-15
108SouthHannah9282024-02-20
=COMBIN(8,2)

Result: 28

Your sales team has 8 unique reps in the log. To assign pairs for joint customer calls, you need to know how many unique partnerships are possible. COMBIN(8,2) returns 28—the number of two-rep combinations (Alice-Bob, Alice-Carol, Bob-Carol, etc.), where the order of selection doesn't matter.

2. Determine region competition matchups

RegionOrders
East2
West2
North2
South2
=COMBIN(4,2)

Result: 6

Your company operates in 4 regions and wants to run a regional sales competition with head-to-head pairings. COMBIN(4,2) returns 6, meaning there are exactly 6 possible matchups: East-West, East-North, East-South, West-North, West-South, and North-South.

3. Plan quality audit samples from order batch

OrderIDUnitsUnitPrice
101525
102350
103830
104275
105640
106460
107735
108928
=COMBIN(8,3)

Result: 56

For quality control, you need to audit 3 orders randomly selected from your batch of 8. COMBIN(8,3) returns 56 possible samples, representing all unique ways to choose 3 orders for inspection without regard to selection sequence.

Common errors

Which COMBIN error are you seeing?
COMBIN returned an error#NUM!
Verify that number_chosen ≤ number. Change =COMBIN(5,8) to =COMBIN(8,5) or reduce the second argument to 5 or fewer.
#VALUE!
Ensure both arguments are numeric. If referencing a text-containing cell, convert with INT() or ROUND(). For example, use =COMBIN(INT(A2),INT(B2)) instead of =COMBIN(A2,B2) if A2 or B2 contain text.
#NUM!
Check that both arguments are zero or positive integers. Verify your data source contains no negative values, or use ABS() to convert negatives to positive if needed.
ErrorWhy it happensHow to fix it
#NUM!The second argument (number_chosen) is greater than the first argument (number), which is impossible—you cannot choose more items than exist.Verify that number_chosen ≤ number. Change =COMBIN(5,8) to =COMBIN(8,5) or reduce the second argument to 5 or fewer.
#VALUE!One or both arguments contain text values instead of numbers, or reference cells with text.Ensure both arguments are numeric. If referencing a text-containing cell, convert with INT() or ROUND(). For example, use =COMBIN(INT(A2),INT(B2)) instead of =COMBIN(A2,B2) if A2 or B2 contain text.
#NUM!Either the number or number_chosen argument is negative; combinations cannot be calculated from negative quantities or items.Check that both arguments are zero or positive integers. Verify your data source contains no negative values, or use ABS() to convert negatives to positive if needed.

Tips and when to use something else

  • COMBIN calculates combinations (order doesn't matter). Use a different function like PERMUT for permutations (order does matter)—COMBIN(5,2)=10 pairs but PERMUT(5,2)=20 ordered arrangements.
  • COMBIN only works with whole numbers. If your data contains decimals, wrap arguments with INT() to truncate them: =COMBIN(INT(A1),INT(B1)).
  • Common real-world scenarios: calculating lottery odds, planning survey sample strategies, determining possible team lineups, or assessing regional competition pairings.
  • Some spreadsheet versions have limits for large inputs; if n>170, COMBIN may return an error or overflow. Break very large calculations into smaller parts if needed.

Related functions

INTINT rounds any number down to the nearest whole integer, always discarding decimal places and rounding toward negative infinity.PRODUCTReturns the product of all numeric values supplied as arguments, multiplying them together into a single result.SUMPRODUCTSUMPRODUCT multiplies arrays element-by-element and sums the results, useful for weighted totals and multi-criteria counting.CHOOSECHOOSE returns the value or range from a list of arguments that corresponds to the supplied index number, letting you pick one of several options.IFERRORIFERROR returns the result of a formula unless that formula generates an error, in which case it returns a user-specified alternative value.

Frequently asked questions

What's the difference between COMBIN and PERMUT?
COMBIN returns the number of combinations—ways to select items where order doesn't matter. PERMUT returns permutations—ways where order does matter. For example, choosing Alice and Bob is the same combination as Bob and Alice (1 combination), but they represent 2 different permutations (1st-2nd vs 2nd-1st). COMBIN(5,2)=10 but PERMUT(5,2)=20.
Can COMBIN work with decimal numbers or fractional values?
No; COMBIN requires integer arguments. If your data contains decimals, convert them first using INT() to truncate or ROUND() to round. For example, =COMBIN(ROUND(A1,0),ROUND(B1,0)) will round both arguments to whole numbers before calculating combinations.
Why do I get #NUM! error when my formula looks correct?
The most common cause is that your second argument (number_chosen) exceeds your first argument (number)—you cannot choose more items than you have. Verify the first argument is greater than or equal to the second. Also check that neither argument is negative.
What's a practical business use of COMBIN?
COMBIN answers questions like: How many ways can we select 2 reps from a team of 8 for joint calls? (28 ways). How many possible samples of 3 orders can we audit from a batch of 100? (161,700 ways). It's invaluable for sampling strategies, lottery odds, team formations, regional matchups, and any scenario requiring 'in how many ways can we select X items from Y total?'

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Reviewed 2026-09-17