AHA vs WHO: two different approaches
The American Heart Association sets fixed sex-specific limits: 36 g (9 teaspoons) per day for men and 25 g (6 teaspoons) for women. These are absolute ceilings, not percentage-based, and are among the strictest mainstream guidelines.
The WHO uses a percentage-of-energy approach, recommending that free sugars stay below 10% of total daily energy—equivalent to around 50 g on a 2,000 kcal diet. Both guidelines target the same outcome: reducing chronic disease risk from excess discretionary sugar.