Techniques and systems described herein provide for improved clock drift calibration of two or more clocks of two or more wireless devices. According to one example method, a first packet is received at a first wireless device from a second wireless device sent at a first time. The method may also include determining a first time-of-arrival estimate for the first packet. The method may further include receiving, at the first wireless device, a second packet from the second wireless device sent at a second time. The method may also include determining a second time-of-arrival estimate for the second packet and determining a relative clock drift between the first wireless device and the second wireless device based at least in part on the first time-of-arrival estimate and the second time-of-arrival estimate.