Microns to phi
Type a value in µm to get it in φ instantly.
9.966φ
Nothing on our list is smaller: clay is 2× coarser. That is clay: too fine to feel as grains.
Convert the other way: φ to µm
What it means
What is that material?
Class boundaries follow the Wentworth scale. Mesh numbers are approximate: sieve standards differ between countries.
The math
How to convert µm to φ
The phi scale is the negative base-two logarithm of the diameter: φ = −log₂(mm), and back the other way, mm = 2^(−φ). Each whole step of phi halves the grain, and the scale runs backwards, so coarse gravel has negative phi.
Example: 1 µm = 9.96578 φ.
Every unit
Your grain size in every unit
Tables
µm to φ conversion table
| µm | φ |
|---|---|
| 0.004 µm | 17.9316 φ |
| 0.016 µm | 15.9316 φ |
| 0.063 µm | 13.9543 φ |
| 0.125 µm | 12.9658 φ |
| 0.25 µm | 11.9658 φ |
| 0.5 µm | 10.9658 φ |
| 1 µm | 9.96578 φ |
| 2 µm | 8.96578 φ |
| 4 µm | 7.96578 φ |
| 16 µm | 5.96578 φ |
| 64 µm | 3.96578 φ |
| 256 µm | 1.96578 φ |
φ to µm conversion table
| φ | µm |
|---|---|
| 0.004 φ | 997.231 µm |
| 0.016 φ | 988.971 µm |
| 0.063 φ | 957.271 µm |
| 0.125 φ | 917.004 µm |
| 0.25 φ | 840.896 µm |
| 0.5 φ | 707.107 µm |
| 1 φ | 500 µm |
| 2 φ | 250 µm |
| 4 φ | 62.5 µm |
| 16 φ | 0.0152588 µm |
| 64 φ | 5.421×10⁻¹⁷ µm |
| 256 φ | 8.636×10⁻⁷⁵ µm |
Quick answers
Quick answers
- How many φ is 1 µm?
- 1 µm is 9.96578 φ.
- How many φ is 10 µm?
- 10 µm is 6.64386 φ.
The units
About these units
Microns (µm)
Thousandths of a millimeter, for silt and clay.
Phi (φ)
The logarithmic scale: −log₂ of the diameter in millimeters. Bigger phi means finer grains.
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