Stirling's Approximation is a mathematical formula used to estimate the factorial of large numbers. It states that for a large positive integer n, the factorial n! can be approximated by the expression n! \approx \sqrt2 \pi n \left( \fracne \right)^n . This approximation simplifies calculations in various fields, including statistics and combinatorics. The formula becomes increasingly accurate as n grows larger, making it particularly useful in situations where calculating the exact factorial is impractical. Stirling's Approximation helps in understanding the growth rate of factorials and is often employed in probability theory and asymptotic analysis.