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Aggregate Fineness Modulus Calculator (ASTM C136)

Compute an aggregate's fineness modulus from a standard sieve analysis, per ASTM C136.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax

Fineness modulus

2.97 (fineness modulus)

High confidence
Sum of cumulative % retained
297 %

Running these inputs gives 2.97 as the fineness modulus. Note that % retained on 3/8 in sieve (cumulative) and % retained on no. 4 sieve (cumulative) sit at the edge of the range this calculator was checked against, so treat the output as indicative rather than settled. Currently reading for United States under IRC 2024 — pick a different market above and the figures re-cast accordingly.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • ASTM C136 fineness modulus: FM = (sum of cumulative percent retained on the standard sieve series: 3/8in, No.4, No.8, No.16, No.30, No.50, No.100) / 100

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Frequently asked questions

What does fineness modulus tell you?
It's a single index number summarizing an aggregate's overall particle size — a higher fineness modulus means coarser (larger average particle size) material, a lower one means finer material.
What's a typical fineness modulus for concrete sand?
ASTM C33 targets 2.3 to 3.1 for fine aggregate used in concrete — sand outside this range can make the mix harder to finish or affect workability and strength.
Do 'cumulative' percentages include everything retained above?
Yes — each sieve's cumulative percentage is the running total of everything retained on that sieve AND all coarser sieves above it, not just what's retained on that one sieve alone.