The correct order of soil particles from smallest to largest is as follows:
- Clay - the smallest soil particles, less than 0.002 mm in diameter.
- Silt - medium-sized particles, ranging from 0.002 mm to 0.02 mm in diameter.
- Sand - larger particles, ranging from 0.02 mm to 2 mm in diameter.
- Gravel - the largest particles, generally greater than 2 mm in diameter.
So, the order from smallest to largest is: Clay, Silt, Sand, Gravel.