One centimetre here and there is really not inconsequential, use an electric measuring tool to be safe. There's no cord to restrict you, just make sure you've charged the battery.
From Amazon
Umarex Laserliner MoistureMaster Compact Plus 082.334A Air and Material Moisture Meters (Measurement of Material Moisture for 56 Wood / 6 Building Materials Types, Data Transfer)
Conrad Electronic
Laserliner MoistureMaster Compact Plus Moisture meter