Site investigation · Laboratory: soil classification

Liquid limit: one-point method calculator

LL from a single Casagrande reading using LL = wN (N/25)^0.121, valid for 20–30 blows.

Standard: AS 1289.3.1.2 · ASTM D4318 Method B

Inputs in the worked example

The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.

Result	Value	Unit
Liquid limit	41.16	%

Diagram for the worked example

Specific gravity (pycnometer) — Two-trial lab sheet for soil particle density with temperature correction to 20 °C and repeatability check.
Particle size distribution — Sieve masses to % passing, grading curve, D10/D30/D60, Cu, Cc and a USCS group symbol.
Hydrometer analysis — Fine-fraction grading from hydrometer readings: particle diameter by Stokes' law and percent finer.
Atterberg limits & plasticity chart — Liquid limit from cone penetrometer or Casagrande points, PI, liquidity index and position on the plasticity…
Moisture, density & phase relations — Bulk and dry density, void ratio, porosity, saturation and field density ratio, with a three-phase diagram.
Moisture content (oven drying) — Moisture content of several specimens from tin masses, with mean, range and repeatability check.
Fines content by washing — Percentage finer than 75 µm from the dry mass before and after washing plus dry sieving of the residue.
Liquid limit: cone penetrometer — Linear fit of moisture content against cone penetration; the liquid limit is w at 20 mm penetration.
Liquid limit: Casagrande cup — Flow curve (w against log N) by least squares; LL at 25 blows and the flow index.
Plastic limit & consistency indices — PL from repeat threads, PI, liquidity and consistency index, activity and plasticity chart class (A-line).

For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.