Soil Textural Triangle Calculator

Calculator Form

Enter one sample or paste batch rows. Leave one fraction blank to auto-balance. Use percentages only.

Sample Name

Sand %

Silt %

Clay %

Batch Rows

Options

Normalize non-100 totals

Example Data Table

Sample	Sand %	Silt %	Clay %	Expected Texture Class	Typical Use Note
Fill A	82	12	6	Sandy Loam	Fast drainage and lower cohesion.
Subgrade B	40	40	20	Loam	Balanced fractions for general site review.
Layer C	18	52	30	Silty Clay Loam	Higher fines and moderate plasticity risk.
Borrow D	55	15	30	Clay Loam	Moderate compaction with notable cohesion.
Pond Edge	12	43	45	Silty Clay	High fines and slower permeability.

Formula Used

The calculator first checks that sand, silt, and clay describe one soil sample. Their combined value must equal 100% after balancing or normalization.

Total percentage: Total = Sand + Silt + Clay

Missing fraction: Missing Value = 100 − Sum of the other two fractions

Normalized fraction: Normalized Value = (Input Value ÷ Total) × 100

Fines percentage: Fines = Silt + Clay

Sand to fines ratio: Sand/Fines Ratio = Sand ÷ (Silt + Clay)

Triangle X coordinate: X = Silt + (Clay ÷ 2)

Triangle Y coordinate: Y = Clay × √3 ÷ 2

The texture class is assigned with rule-based textural triangle boundaries commonly used for sand, silt, and clay interpretation in practice.

How to Use This Calculator

Enter the sample name for single-sample review.
Type sand, silt, and clay percentages.
Leave one fraction empty if you want auto-balancing.
Enable normalization when lab totals do not equal 100.
Use batch rows to compare multiple site materials together.
Press the calculate button.
Review the texture class, dominant fraction, fines percentage, and coordinates.
Check the Plotly triangle graph for sample placement.
Download CSV for spreadsheet work or PDF for reporting.

FAQs

1. What does the soil textural triangle measure?

It classifies soil by the percentage of sand, silt, and clay. The triangle helps identify texture groups that affect drainage, compaction, cohesion, and construction handling.

2. Can I leave one field empty?

Yes. If two fractions are provided, the calculator can balance the missing value so the total becomes 100%. This helps when one lab fraction is not listed.

3. What happens if my totals do not equal 100?

When normalization is enabled, the calculator rescales all three fractions to 100%. This keeps the sample usable while preserving the original proportion pattern.

4. Why is fines percentage important?

Fines combine silt and clay. Higher fines often indicate lower permeability, higher moisture sensitivity, and stronger effects on compaction behavior and field performance.

5. Is this useful for construction work?

Yes. Texture review can support fill selection, drainage planning, subgrade review, erosion control checks, and quick comparisons between borrow sources or site layers.

6. Can I compare many samples together?

Yes. Paste batch rows in the textarea using comma-separated values. The calculator will process valid rows, classify each one, and plot them together.

7. What does the triangle graph show?

It plots each sample using sand, silt, and clay percentages on a ternary triangle. This helps visualize how close samples are to each textural region.

8. Are the class boundaries exact laboratory standards?

The calculator uses rule-based triangle boundaries for practical classification. It is strong for screening and reporting, but final design decisions should still follow project testing standards.