12/15 as a Decimal 0.8 12/15 = 0.8 = 80% Copy 12/15 = 0.8 = 80%. Simplified: 4/5. Formula Used12 ÷ 15 = 0.8 Frequently Asked Questions What is 12/15 as a decimal?0.8.What is 12/15 as a percentage?80%.