For a rough test, Android has software called Ampere, which measures the current charged to the battery, multiplied by the current time of the battery voltage is the power to charge the battery. The actual power is slightly higher, because there is no calculation of the standby power consumption of the phone, the efficiency of the wireless coil reception, and the efficiency of the internal buck module of the phone.
ios I know there is a software called batterylife can achieve the same function, but to jailbreak, and some mobile phone bright screen charging power will be reduced, this time you can use a USB ammeter to measure the charging head output power, multiplied by about 70% is probably the actual power of wireless charging.