What is 1% of 40? 0.4 1% of 40 Copy 1% of 40 = 0.4. Formula UsedResult = (1 ÷ 100) × 40 = 0.4 Frequently Asked Questions What is 1% of 40?0.4. (1 ÷ 100) × 40 = 0.4.How to calculate 1%?Multiply by 0.01 (or multiply by 1 then divide by 100).