Creating smartphone applications for more than one operating system requires knowledge of several code languages, more code maintenance, higher development costs and longer development time. To make this easier cross-platform tools (CPTs) exist. But using a CPT can decrease performance of the application. Applications with low performance are more likely to get uninstalled and this makes developers lose income. There are four main CPT approaches hybrid, interpreter, web and cross-compiler. Each has different disadvantages .and advantages. This study will examine the performance difference between two CPTs, Codename One and PhoneGap. The performance measurements, CPU load, memory usage, energy consumption, time execution and application size will be made to compare the CPTs. If cross-compilers have better performance than other CPT approaches will also be investigated. An experiment where three applications are created with native Android, Codename One and PhoneGap will be made and performance measurements will be made. A literature study with research from IEEE and Engineering village will be conducted on different CPT approaches. PhoneGap performed best with shortest execution time, least energy consumption and least CPU usage while Codename One had smallest application size and least memory usage. The research available on performance for CPTs is short and not well done. The difference between PhoneGap and Codename One is not big except for writing to SQLite. No basis was found for the statement that cross-compilers have better performance than other CPT approaches.