8/20 as a Decimal 0.4 8/20 = 0.4 = 40% Copy 8/20 = 0.4 = 40%. Simplified: 2/5. Formula Used8 ÷ 20 = 0.4 Frequently Asked Questions What is 8/20 as a decimal?0.4.What is 8/20 as a percentage?40%.