Fineness modulus

The Fineness Modulus (FM) is an empirical figure obtained by adding the total percentage of the sample of an aggregate retained on each of a specified series of sieves, and dividing the sum by 100. Sieves sizes are: 150-μm (No. 100), 300-μm (No. 50), 600-μm (No. 30), 1.18-mm (No. 16), 2.36-mm (No. 8), 4.75-mm (No. 4), 9.5-mm (3/8-in.), 19.0-mm (3/4-in.), 37.5-mm (11/2-in.), and larger, increasing in the ratio of 2 to 1. The same value of fineness modulus may therefore be obtained from several different particle size distributions. In general, however, a smaller value indicates a finer aggregate. Fine aggregates range from an FM of 2.00 to 4.00, and coarse aggregates smaller than 38.1 mm range from 6.75 to 8.00. Combinations of fine and coarse aggregates have intermediate values.[1]

Fineness modulus of combined aggregatesEdit

Fineness modulus of combined aggregates is always between the Fineness modulus of aggregates and combined modulus coarse aggregate have intermediate value. it is given by the formula.



  is resultant fineness modulus
  is fineness modulus of fine aggregate
  is fineness modulus of coarse aggregate
  is proportion of fine aggregate in combined aggregate

ratio X of fine aggregate on coarse aggregate in combined aggregate can be found by:[2]


proportion of fine aggregate Y in percentage can be calculated by:[3]


Put X value



Fineness modulus

  1. ^ "Method of calculation of the Fineness modulus of aggregate" (PDF). Whole Building Design Guide. National Institute of Building Science. 1980-03-01. Archived from the original (PDF) on 2010-06-21. Retrieved 2010-12-12.
  2. ^
  3. ^

Fineness modulus and its calculation ASTM C136,