How to use the soil plasticity index calculator
Find the plasticity index of a soil from its liquid limit and plastic limit. Enter liquid limit, plastic limit in the fields above; the plasticity index, soil behaviour are computed instantly and plotted on the chart so you can see how the answer changes.
Common searches this calculator answers include “plasticity index soil”, “Atterberg limits”, “liquid limit minus plastic limit”, “calculate soil plasticity index”, “find plasticity index”.
Formula
Variables
- LL — Liquid limit (%)
- PL — Plastic limit (%)
Worked example
With liquid limit = 45 %, plastic limit = 22 %, the calculator gives plasticity index ≈ 23 %; soil behaviour ≈ Plastic clay-rich soil text.
Frequently asked questions
What is the soil plasticity index calculator used for?
Find the plasticity index of a soil from its liquid limit and plastic limit. It helps with questions such as “plasticity index soil”, “Atterberg limits”, “liquid limit minus plastic limit”.
What is the formula for the soil plasticity index calculation?
Plasticity index (%) = LL-PL. Soil behaviour (text) = [Plasticity index]>15?"Plastic clay-rich soil":"Low plasticity soil". Here LL is liquid limit (%), PL is plastic limit (%).
What inputs do I need for the soil plasticity index calculator?
You need liquid limit in %, plastic limit in %. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use the soil plasticity index calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the soil plasticity index result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.