Millimeters to phi
Type a value in mm to get it in φ instantly.
0φ
That's 2.9× as coarse as medium sand, while gravel is 4× coarser. That is sand: individual grains you can see.
Convert the other way: φ to mm
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 mm 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 mm = 0 φ.
Every unit
Your grain size in every unit
Tables
mm to φ conversion table
| mm | φ |
|---|---|
| 0.004 mm | 7.96578 φ |
| 0.016 mm | 5.96578 φ |
| 0.063 mm | 3.9885 φ |
| 0.125 mm | 3 φ |
| 0.25 mm | 2 φ |
| 0.5 mm | 1 φ |
| 1 mm | 0 φ |
| 2 mm | -1 φ |
| 4 mm | -2 φ |
| 16 mm | -4 φ |
| 64 mm | -6 φ |
| 256 mm | -8 φ |
φ to mm conversion table
| φ | mm |
|---|---|
| 0.004 φ | 0.997231 mm |
| 0.016 φ | 0.988971 mm |
| 0.063 φ | 0.957271 mm |
| 0.125 φ | 0.917004 mm |
| 0.25 φ | 0.840896 mm |
| 0.5 φ | 0.707107 mm |
| 1 φ | 0.5 mm |
| 2 φ | 0.25 mm |
| 4 φ | 0.0625 mm |
| 16 φ | 1.526×10⁻⁵ mm |
| 64 φ | 5.421×10⁻²⁰ mm |
| 256 φ | 8.636×10⁻⁷⁸ mm |
Quick answers
Quick answers
- How many φ is 1 mm?
- 1 mm is 0 φ.
- How many φ is 10 mm?
- 10 mm is -3.32193 φ.
The units
About these units
Millimeters (mm)
The plain diameter of a grain.
Phi (φ)
The logarithmic scale: −log₂ of the diameter in millimeters. Bigger phi means finer grains.
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