In more detail
The coefficient is 500 / (a + b·x + c·x² + d·x³ + e·x⁴ + f·x⁵), where x is body weight in kilograms and the six constants differ for men and women. The score is the lifter's total, the best squat plus bench press plus deadlift, multiplied by that coefficient. An updated version was published in 2020, and many federations have moved to other formulas: the IPF uses its own GL points and DOTS is widespread elsewhere.
Why it matters
It decides "best lifter" awards across weight classes, where heavier lifters naturally move more weight. Critics argued the original curve favoured some body weights over others, which is why it has been replaced in many places. Scores from different formulas are not comparable, so always state which one was used.
Example
Original Wilks coefficients:
Man, 83 kg, total 600 kg: coefficient 0.6675 → 600 × 0.6675 = 400.5
Man, 120 kg, total 700 kg: coefficient 0.5749 → 700 × 0.5749 = 402.4
Woman, 63 kg, total 400 kg: coefficient 1.0740 → 400 × 1.0740 = 429.6
The heavier man lifts 100 kg more but scores only 1.9 points higher.