What is 20% of 90? 18 20% of 90 Copy 20% of 90 = 18. Formula UsedResult = (20 ÷ 100) × 90 = 18 Frequently Asked Questions What is 20% of 90?18. (20 ÷ 100) × 90 = 18.How to calculate 20%?Multiply by 0.2 (or multiply by 20 then divide by 100).