Off the Charts:

If something is “off the charts” it means that it is too big to even measure, or “unusually large in some way”.

If a person weighs 250 kg, you could say that their weight is “off the charts“.  It’s “too big to measure” or “too big for a normal scale to measure”.

Her singing is amazing.  It’s off the charts.

I can’t believe how stupid he is.  It’s just off the charts!

His strength is off the charts.  He’s the strongest person I’ve ever seen.