order of magnitude 
noun
1A class in a system of classification determined by size, typically in powers of ten: the forces between atoms on a polymer chain are about two orders of magnitude stronger than those between chains...
- To measure changes that take place in about a femtosecond, they needed something they could characterize in attoseconds, an order of magnitude lower than existing systems.
- As late as 1997 unemployment rates remained over 10 per cent, an order of magnitude higher than in the golden age of the 1960s and more than twice the rates of the United States.
- Both these estimates were an order of magnitude too small, but the fault was in Aristarchus's lack of accurate instruments rather than in his correct method of reasoning.
1.1Size or quantity: the new problems were of a different order of magnitude...
- We are dealing with a different order of magnitude of threat.
- I was bowled away by the band's performance last year, but this was a different order of magnitude.
- But Mont Pincon was different, the same sort of battle but of a different order of magnitude.