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 OnBuy
Amprobe PM55A Pocket Multimeter
Acme Tools
Amprobe PM55A 600V AC/DC Pocket Multimeter
Rapid Online
Amprobe PM55A Pocket Multimeter