Geology Wentworth Grain Size Phi Calculator
Actual weighted grain distribution phi=−log2(d/mm), signed coarse coordinates retained. Caller independently establishes matching units, evidence, method edition and applicability; output is not compliance, diagnosis, work-safety approval, geological identity or validated hazard prediction.
Description
A phi value is the negative base-two logarithm of grain diameter measured in millimeters.
A phi value is the negative base-two logarithm of grain diameter measured in millimeters.1
Averaging phi values with weights summarizes a size distribution on a logarithmic scale rather than averaging diameters directly. Use this tool to calculate wentworth grain size phi from the supplied measurements and assumptions.
When to use Geology Wentworth Grain Size Phi Calculator
Use this tool to calculate wentworth grain size phi from the supplied measurements and assumptions. Establish the measurement units, sampled interval, calibration or model edition and geological assumptions before entering data.
How to use Geology Wentworth Grain Size Phi Calculator and understand its results
- Establish the measurement units, sampled interval, calibration or model edition and geological assumptions before entering data.
- Enter grainDiametersMm, grainMassWeights, using the field meanings and rules below, then run the tool.
- Read phi, weightedMeanPhi. Interpret the fields using their units, signs and evidence conventions below.
- If input validation fails, correct the reported field and run again. Before applying the result, check reference scope, model assumptions and any missing evidence or placeholder values.
| Input field | Meaning | Value type | Requirement |
|---|---|---|---|
| grainDiametersMm | Grain diameters mm | list of number | Required |
| grainMassWeights | Grain mass weights | list of number | Required |
Enter nonempty aligned positive diameters in millimeters and nonnegative mass weights with positive total weight. Convert each diameter to −log2(diameter), then take the weighted mean of those phi values. Zero weights contribute nothing; the tool does not reconstruct a full cumulative grain-size distribution.
phi_i=−log2(d_i in mm); meanPhi=Σ(weight_i×phi_i)/Σweights Use the exact units, boundary rules, ordering and missing-evidence conventions above.
| Output field | Meaning | Value type |
|---|---|---|
| phi | Phi; follow the units, sign, ordering and evidence convention stated above | list of number |
| weightedMeanPhi | Weighted Mean Phi; follow the units, sign, ordering and evidence convention stated above | number |
{
"input": {
"grainDiametersMm": [
0.5,
1,
2
],
"grainMassWeights": [
1,
2,
1
]
},
"output": {
"phi": [
1,
0,
-1
],
"weightedMeanPhi": 0
}
}Limitations and assumptions
Averaging phi values with weights summarizes a size distribution on a logarithmic scale rather than averaging diameters directly. Interpretation depends on the units, sampling scope and exact model described above.
All listed fields require explicit values. Unexpected fields, incorrect types, nonfinite numbers and sparse evidence arrays fail validation; the specific bounds and alignment requirements are stated above. Extremely large inputs or outputs can also be rejected. An input error is distinct from a successful result reporting false, no matches or missing evidence.
Alternative or Complementary methods
Use Geology Wentworth Phi To Mm Calculator for this related task: The phi grain-size scale is logarithmic, with increasing phi corresponding to decreasing diameter.
Use Geology Sorting Coefficient Trask Calculator when its separate inputs and assumptions fit the question: The Trask sorting coefficient compares two diameter percentiles through their ratio.
References
Similar or alternative tools
- Geology Wentworth Phi To Mm Calculator
The phi grain-size scale is logarithmic, with increasing phi corresponding to decreasing diameter.
- Geology Sorting Coefficient Trask Calculator
The Trask sorting coefficient compares two diameter percentiles through their ratio.