What is 10% of 40? 4 10% of 40 Copy 10% of 40 = 4. Formula UsedResult = (10 ÷ 100) × 40 = 4 Frequently Asked Questions What is 10% of 40?4. (10 ÷ 100) × 40 = 4.How to calculate 10%?Multiply by 0.1 (or multiply by 10 then divide by 100).