order of magnitude

noun

• a class in a system of classification determined by size, each class being a number of times (usually ten) greater or smaller than the one before:values might be compared by order of magnitude, a staple in making ballpark estimates
• relative size, quantity, quality, etc.:the new problems were of a different order of magnitude
• the arrangement of a number of items determined by their relative size:the items are arranged in ascending order of magnitude