What is 4% of 20? 0.8 4% of 20 Copy 4% of 20 = 0.8. Formula UsedResult = (4 ÷ 100) × 20 = 0.8 Frequently Asked Questions What is 4% of 20?0.8. (4 ÷ 100) × 20 = 0.8.How to calculate 4%?Multiply by 0.04 (or multiply by 4 then divide by 100).