What is 80% of 90? 72 80% of 90 Copy 80% of 90 = 72. Formula UsedResult = (80 ÷ 100) × 90 = 72 Frequently Asked Questions What is 80% of 90?72. (80 ÷ 100) × 90 = 72.How to calculate 80%?Multiply by 0.8 (or multiply by 80 then divide by 100).