In this paper, we compare asynchronous circuits from register transfer level (RTL) conversion and gate level (GL) conversion for synchronous circuits. Through the comparison, we show which conversion is better for asynchronous circuits. We also describe the design methods for asynchronous circuits from RTL conversion and GL conversion. The experimental result showed that RTL conversion results in better asynchronous circuits than GL conversion in terms of energy consumption. On average, 11.3% energy consumption was reduced compared to the synchronous counterparts.