What is 90% of 80? 72 90% of 80 Copy 90% of 80 = 72. Formula UsedResult = (90 ÷ 100) × 80 = 72 Frequently Asked Questions What is 90% of 80?72. (90 ÷ 100) × 80 = 72.How to calculate 90%?Multiply by 0.9 (or multiply by 90 then divide by 100).