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Concrete Slump Flow Test Calculator (ASTM C1611)

Classify a self-consolidating concrete (SCC) mix's flowability and viscosity from a slump flow test reading.

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

Average slump flow

26.57 in

High confidence

Flowability class: SF2. Viscosity class: VS2 (more viscous, better segregation resistance).

Diameter spread between the two readings
0.39 in
T50 spread time
3 s

With the figures above, the average slump flow comes to 675 mm. Behind that figure, diameter spread between the two readings is the biggest single quantity at 10 mm; start there if the total looks wrong. This is calculated for United States and cites IRC 2024. Building in another market? Change the selector above so the units and code reference follow.

Add the equipment this sizes

This result is a specification — 26.575 in — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

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 C1611 slump flow test procedure and EFNARC/ACI SF1-SF2-SF3 flowability classes (SF1: 550-650mm, SF2: 651-750mm, SF3: 751-850mm) and VS1/VS2 viscosity classes based on the T50 spread time (VS1 ≤ 2s, VS2 > 2s)

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Frequently asked questions

What does the slump flow diameter tell me?
It's a direct measure of the mix's flowability under its own weight — larger spread means a more flowable mix, useful for congested reinforcement or complex formwork, but excessive spread can also signal segregation.
Why does T50 (spread time) matter separately from the final diameter?
Two mixes can reach the same final spread diameter at very different speeds — T50 measures viscosity, which affects how the mix behaves while filling formwork and how much time workers have before it locks in place.
What is a Visual Stability Index (VSI)?
A separate 0-3 visual rating (not calculated here) for segregation signs like a mortar halo around the patty's edge or coarse aggregate piling at the center — always inspect the actual test patty, since numbers alone don't catch every segregation sign.