What is 20% of 40? 8 20% of 40 Copy 20% of 40 = 8. Formula UsedResult = (20 ÷ 100) × 40 = 8 Frequently Asked Questions What is 20% of 40?8. (20 ÷ 100) × 40 = 8.How to calculate 20%?Multiply by 0.2 (or multiply by 20 then divide by 100).