42/64 as a Decimal 0.65625 42/64 = 0.65625 = 65.625% Copy 42/64 = 0.65625 = 65.625%. Simplified: 21/32. Formula Used42 ÷ 64 = 0.65625 Frequently Asked Questions What is 42/64 as a decimal?0.65625.What is 42/64 as a percentage?65.625%.