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Fineness modulus (FM) calculator
Enter the mass retained on each sieve from your sand gradation and get % retained, cumulative % retained, % passing, and the fineness modulus as you type.
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Fineness modulus —
Enter the mass retained on each sieve to see results.
| Sieve | Retained (g) | % retained | Cum. % retained | % passing | Counts toward FM |
|---|---|---|---|---|---|
| No results yet. | |||||
What fineness modulus tells you
Fineness modulus is a single number that sums up how coarse or fine an aggregate is. Add up the cumulative percentages retained on the standard sieves (No. 100, 50, 30, 16, 8, 4, 3/8 in., and any coarser standard sieves used) and divide by 100. A higher FM means a coarser sand; a lower FM means a finer one. The No. 200 sieve and the pan never count toward FM.
For block, pavers, and retaining wall units, a shift in sand FM can show up as changes in texture, density, and how the mix handles in the machine, so tracking it from load to load is a useful habit.
A quick check, not a full test. This calculator is a convenient way to run the numbers. It isn't a substitute for a full ASTM C136 sieve analysis performed as the standard describes, or for your own QC plan.
Watch the video: Bubba walks through a sieve analysis and the fineness modulus (about 7 minutes, with captions and a transcript).
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