Concrete Grade M20: Strength, Mix Ratio, and Uses
M20 concrete reaches a characteristic cube strength of 20 newtons per square millimeter at 28 days. Here is what goes into it and where it belongs.
Characteristic strength: 20 N/mm² cube at 28 days
| Grade designation | M20 |
| Characteristic cube strength | 20 N/mm² |
| Approximate cylinder strength | 16 N/mm² |
| Mix | 1:1.5:3 nominal |
| Typical cement content | about 400 kg, 8 bags per cubic meter |
| Typical uses | reinforced slabs, beams, and columns in ordinary housing |
Notes for design and site
M20 is the minimum grade most codes allow for reinforced concrete in mild exposure, which makes it the default for modest residential frames. Beyond a story or two, or anywhere near a coast, designers move up a grade. Cure it properly: M20 gains a third of its strength after the first week.
Related Calculators and Reference
- Concrete Mix Proportions and Yield: turn these ratios into bags and cubic meters.
- Construction Cost Risk Calculator: budget the pour with honest uncertainty.
- American Concrete Institute: authoritative concrete practice.