every quality charger should have the output voltage and current printed on it.
As far as apps go, battery monitor widget by 3c is pretty accurate. I have used it for years with other HTC devices. It will show the current input when charging and current drain when unplugged.
So FYI,
Stock charger has an output current of 1Amp. or 1000mA. Most standard USB ports on computers have 500mA output.
You can also charge it with a 2Amp charger as the device will limit itself from drawing to much current.
If i had to guess id say your using 500mA or 750mA charger now.