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CONCRETE CURING & POUR PLANNING · CONCRETE COMPRESSIVE STRENGTH CALCULATOR

Compressive Strength of Concrete Cylinder

Cylinder strength = failure load ÷ the end area. A 150 × 300 mm cylinder has 17,671 mm², so 500 kN gives 28.3 MPa. A 4 × 8 in cylinder of 4,000 psi concrete fails at about 50.3 kips. Cylinder strength is about 0.8 times cube strength.

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Test
kN
Concrete
MPa
Compression test28.3 MPa at 28 daysCylinder between platensmyconstructioncalculator.comNot to scale
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Results

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Compressive strength
28.3MPa
In psi4,104 psi
Expected mean at 28 days33.0 MPa
Result ÷ expected86 %
Result ÷ specified strength113 %

Cylinder strength is lower than cube strength: compare with f'c (ACI) or the first number of EN C25/30.

Acceptance uses groups of results, not one specimen: see IS 456 Table 11 or ACI 318 §26.12.3.

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Working
  1. Loaded area of a 150 × 300 mm cylinder = 17,671 mm² (27.39 in²)
  2. Strength = 500.0 kN ÷ area = 28.3 MPa
  3. Expected mean = (specified + 8 MPa) × exp{0.25 × [1 − √(28 ÷ 28)]} = 33.0 × 1.000 = 33.0 MPa (EN 1992-1-1 Eq. 3.2, standard 20 °C curing)
Results are estimates for planning and material ordering only. They are not a substitute for structural design or approval by a qualified engineer. Read the full disclaimer.
Formula


Strength = failure load ÷ (π/4 × diameter²)
150 × 300 mm: 17,671 mm²      6 × 12 in: 28.27 in²      4 × 8 in: 12.57 in²


Worked Example


A 150 × 300 mm cylinder fails at 500 kN:


    

  1. Area = π/4 × 150² = 17,671 mm²
    2. 

  2. Strength = 500,000 ÷ 17,671 = 28.3 MPa (4,104 psi)
    3. 



Failure Load for f’c (ACI)






f’c
4 × 8 in cylinder
6 × 12 in cylinder






3,000 psi
37.7 kip
84.8 kip




4,000 psi
50.3 kip
113.1 kip




5,000 psi
62.8 kip
141.4 kip






Cylinder and Cube Strength (EN 206 Classes)






Class
Cylinder
Cube






C20/25
20 MPa
25 MPa




C25/30
25 MPa
30 MPa




C30/37
30 MPa
37 MPa




C35/45
35 MPa
45 MPa




C40/50
40 MPa
50 MPa






More Concrete Strength Tests
Frequently Asked Questions
How many cylinders make one strength test?
Under ACI 318 §26.12.1, a strength test is the average of two 6 × 12 in cylinders or three 4 × 8 in cylinders from the same sample, tested at 28 days unless specified otherwise.
Why does EN write classes as C25/30?
The first number is the characteristic cylinder strength and the second the cube strength, both in MPa. C25/30 means 25 MPa on cylinders and 30 MPa on cubes.
Can I convert cylinder strength to cube strength?
Roughly, cube ≈ cylinder ÷ 0.8 for normal concrete, as the EN classes show. It is an approximation: test the specimen type your specification asks for.
References
  • EN 1992-1-1 Eq. 3.2 (strength development) and Table 3.1 (fcm = fck + 8 MPa)
  • IS 516 (cube tests), ASTM C39 (cylinder tests); acceptance: IS 456:2000 Table 11, ACI 318-19 §26.12.3