In this paper, two new compacts halved size single and UWB antennas are proposed for WiFi and UWB applications. The single-band compact halved size slot antenna is proposed for WiFi applications at 2.4 GHz. The resonant frequency of the conventional slot antenna can be reduced by cutting the antenna into two halves and without using any lumped elements inside the slot. Moreover, the impedance and radiation characteristics of the proposed halved-size antenna are suitable for WiFi applications at 2.4 GHz. The proposed WiFi antenna has a miniaturized size of 25 × 16.5 × 0.813 mm³. Then, an octagonal blended-shape antenna (OBSA) for UWB applications is proposed. By applying the same cutting concept, the halved size OBSA covers the UWB band from 3.1 GHz to 10.6 GHz. Furthermore, a grounded L-stub is added on the top side to improve the reflection coefficient. The proposed OBSA has a compact size of 28 × 13 × 0.813 mm³ with stable omnidirectional radiation patterns. Simulation and measured results are in good agreement.