What is 15% of 20? 3 15% of 20 Copy 15% of 20 = 3. Formula UsedResult = (15 ÷ 100) × 20 = 3 Frequently Asked Questions What is 15% of 20?3. (15 ÷ 100) × 20 = 3.How to calculate 15%?Multiply by 0.15 (or multiply by 15 then divide by 100).