Excel like a finance pro.
← The libraryPractice · 2 questions →
Math function
FACTDOUBLE
Returns the double factorial of a number, the product of every other integer down to 1.
Rarely usedDifficulty 1300 · ProficientUsage rank #303 of 520
When to use it
Double factorial: n × (n-2) × (n-4) … down to 1 or 2.
The shape of it
- Syntax
=FACTDOUBLE(number)
Worked examples
Even
=FACTDOUBLE(6) → 48
6 × 4 × 2.
Odd
=FACTDOUBLE(7) → 105
7 × 5 × 3 × 1.
Zero
=FACTDOUBLE(0) → 1
By definition.
Worth knowing
- Counts perfect matchings: 2n-1 double factorial pairs up 2n people.
- Non-integers are truncated.
- Appears in moments of the normal distribution.
Where it goes wrong
- #NUM! for negative input.
- Overflows for large n.
Related
Learn the moves here — or let Wauvel run them on your numbers.
Meet your AI CFO →One CFO-grade Excel tip a week
A short, practical email for finance operators — functions, shortcuts, and the moves that save an afternoon. Free, unsubscribe anytime.