What is 9% of 90? 8.1 9% of 90 Copy 9% of 90 = 8.1. Formula UsedResult = (9 ÷ 100) × 90 = 8.1 Frequently Asked Questions What is 9% of 90?8.1. (9 ÷ 100) × 90 = 8.1.How to calculate 9%?Multiply by 0.09 (or multiply by 9 then divide by 100).