What is the comes first kilogram hecagram decagram then gram etc?

Answer 1

In SI measurements, a whole has no prefix.

Getting smaller progressively from the whole, the prefixes go: deci-, centi-, milli-, micro-, nano-, pico-.

Getting progressively bigger from the whole, the prefixes go: deca-, hecto-, kilo-, mega-, giga-, tera-.

So gram comes first as it is the unit. The others are just multiples of this unit to make the numbers easier.

Answer 2

The order from largest to smallest is tonne, kilogram, hectogram, decagram, gram, decigram, centigram, and milligram.