Concrete PSI to MPa Converter

Enter a compressive strength value in PSI or MPa to instantly convert between units. Includes ACI to EN grade equivalents, mix design guidance, and a full reference table for the most common concrete strengths.

Free to use No sign-up required ASTM C39 exact conversion factor Converts both directions

✓ PSI → MPa and MPa → PSI ✓ ACI & EN grade lookup ✓ Common strength presets ✓ Last verified May 2026

Reviewed by the AllConcreteCalculator.com editorial team — conversion factor cross-checked against ASTM C39 and ACI 318, May 2026.

Enter Compressive Strength

Compressive Strength Value

Enter the specified 28-day compressive strength (f'c). Common US values: 3000, 3500, 4000, 5000 PSI. Please enter a valid strength value greater than 0.

Quick Select — Common US Grades

Or enter MPa / ksi / kgf/cm² and select unit above.

Results appear instantly. No sign-up required.

Converted Strength Values

Converted Values

—

MPa (N/mm²)

—

PSI (lb/in²)

—

ksi (kip/in²)

— kgf/cm²

— ACI Grade (f'c)

— EN 206 Grade

— Use Category

Exact conversion factor (ASTM / SI): 1 PSI = 0.00689476 MPa
Inverse: 1 MPa = 145.0377 PSI

PSI → MPa: MPa = PSI × 0.00689476
MPa → PSI: PSI = MPa × 145.0377
PSI → ksi: ksi = PSI ÷ 1000
PSI → kgf/cm²: kgf/cm² = PSI × 0.0703070

Note: The rounded approximation "1 MPa ≈ 145 PSI" is acceptable for field use.
The exact factor 145.0377 is used here for engineering-grade precision.

How to Use This PSI to MPa Converter

Locate the specified compressive strength on your drawings or mix design. On US plans this is labeled f'c and expressed in PSI — typically 3,000, 3,500, 4,000, or 5,000 PSI for residential and commercial work. On international or metric drawings it will appear in MPa (also written N/mm²). Look for it in the concrete notes block or the structural general notes.
Enter the value and select the correct unit from the dropdown. The calculator accepts PSI, MPa, ksi (kilopounds per square inch), and kgf/cm² (the older metric unit still common in Latin America and parts of Asia). Use the quick-select buttons for the four most common US grades to avoid typing errors.
Read all converted values from the results panel. The primary card shows MPa. The secondary cards show PSI and ksi. The summary row includes kgf/cm², the nearest standard ACI f'c grade, the equivalent EN 206 concrete class, and a plain-English use category so you can quickly verify the grade is appropriate for your application.
Use the EN 206 grade when ordering from a European or metric supplier. When coordinating with international suppliers or reviewing metric structural drawings, give the EN C-class (e.g. C25/30) to the batch plant rather than a raw MPa number — the C-class also communicates the characteristic cylinder vs cube strength pairing, which prevents mix design errors on international projects.

⚠ Pro Tip: The most common error on cross-border projects is confusing cylinder strength (used in the US — ASTM C39) with cube strength (used in Europe — EN 12390-3). The EN C25/30 grade means 25 MPa cylinder / 30 MPa cube. If a European mix design says 30 MPa, don't automatically treat that as the equivalent of 4,350 PSI — it may be a cube strength, which is roughly 80% of the cylinder value. Always confirm which test method applies before specifying concrete on international projects.

PSI to MPa Conversion Formula

The conversion between PSI and MPa is a straightforward unit substitution using the exact SI definition. One pound-force per square inch equals exactly 6,894.757 Pascals, which is 0.006894757 MPa. The table below shows both directions and a worked example for the four most common US concrete grades.

Step	Formula	Example (4,000 PSI)
1. Start with PSI value	f'c in PSI	4,000 PSI
2. Apply exact conversion	PSI × 0.00689476	4,000 × 0.00689476
3. Result in MPa	= MPa value	= 27.58 MPa
4. Round for spec use	Nearest 0.1 MPa	27.6 MPa

Common Concrete Strength Reference Table

Pre-calculated conversions for the most common concrete compressive strengths used in US and international practice.
PSI	MPa	ksi	kgf/cm²	EN 206 Class	Typical Use
2,500	17.2	2.50	175.8	C16/20	Non-structural fill, lean concrete
3,000	20.7	3.00	210.9	C20/25	Sidewalks, patios, footings
3,500	24.1	3.50	246.1	C25/30	Residential driveways, garage floors
4,000	27.6	4.00	281.2	C25/30	Commercial slabs, structural walls
4,500	31.0	4.50	316.4	C30/37	Structural columns, post-tensioned
5,000	34.5	5.00	351.5	C32/40	High-rise columns, bridge decks
6,000	41.4	6.00	421.8	C35/45	Precast, post-tensioned beams
8,000	55.2	8.00	562.5	C45/55	High-strength structural elements
10,000	68.9	10.00	703.1	C55/67	High-performance concrete (HPC)
12,000	82.7	12.00	843.7	C67/82	Ultra-high-performance (UHPC)

EN 206 cylinder/cube strength classes shown. The EN class uses characteristic cylinder strength for the C designation. Exact PSI-to-EN mapping is approximate — consult project specifications for exact grade equivalency on international work.

Which Concrete Strength Grade Do I Need?

Selecting the right compressive strength is one of the most consequential decisions in concrete specification. Too low and the slab or structure will fail under load or weather; too high and you're paying significantly more than necessary. The table below reflects ACI 318 and industry-standard recommendations for common applications.

Recommended concrete compressive strength (f'c) by application type — US practice (ACI 318).
Application	Min f'c (PSI)	Equiv. MPa	EN Class	Notes
Non-structural fill / lean concrete	2,000–2,500	13.8–17.2	C12/15–C16/20	No structural role
Sidewalk / walkway	3,000	20.7	C20/25	Foot traffic only
Residential patio / slab-on-grade	3,000	20.7	C20/25	Add wire mesh or rebar
Residential driveway	3,500	24.1	C25/30	4,000 PSI in freeze-thaw zones
Garage floor	3,500	24.1	C25/30	Rebar recommended
Commercial / industrial floor	4,000	27.6	C25/30	Fiber reinforcement common
Foundation walls / footings	3,000	20.7	C20/25	4,000 PSI if soil is aggressive
Structural columns / beams	4,000–5,000	27.6–34.5	C25/30–C32/40	Engineer to specify
Bridge decks / parking structures	5,000	34.5	C32/40	Air entrainment required
Precast / post-tensioned elements	5,000–6,000	34.5–41.4	C32/40–C35/45	Higher early strength needed
High-performance / UHPC	8,000+	55.2+	C45/55+	Specialist mix design required

In freeze-thaw climates (USDA Hardiness Zones 1–6 and most of Canada), always specify a minimum of 4,000 PSI (27.6 MPa) for any exposed exterior concrete — regardless of what the table says for a given application. Pair it with 5–7% air entrainment. Using 3,000 PSI outdoors in a climate where temperatures cycle below freezing is a specification error that will produce scaling and spalling within 5–10 years.

Common Mistakes When Working with PSI and MPa

⚠️
Confusing cylinder strength with cube strength. US concrete is tested in cylinders (ASTM C39). European concrete uses cubes (EN 12390-3). A cube test gives roughly 20–25% higher results than a cylinder test on the same mix. The EN C25/30 designation means 25 MPa cylinder / 30 MPa cube. If you treat the cube strength as the design strength, you're under-specifying by about 20%.
📐
Using the rounded approximation on structural calculations. The common shortcut "1 MPa ≈ 145 PSI" is fine for quick field checks and verbal communication. But for structural calculations, elastic modulus formulas, and mix design submittals, always use the exact factor: 1 PSI = 0.00689476 MPa. The rounding error is small per unit but compounds significantly in formulas where f'c appears under a square root.
🏗️
Specifying the same grade for all elements on a project. It's tempting to call out a single f'c for the whole job to simplify ordering. But concrete columns in a high-rise may need 6,000–8,000 PSI, while the slab-on-grade needs only 3,500 PSI. Over-specifying expensive high-strength concrete for flatwork is wasteful; under-specifying structural members is dangerous. Use appropriate strengths by element type.
🌡️
Specifying f'c without specifying the test age. Compressive strength is almost always a 28-day value (f'c at 28 days). But some specifications use 56-day or 90-day strengths for mass concrete or slow-gain supplementary cementitious materials (SCMs) like fly ash or slag. If you specify "30 MPa concrete" without an age, the batch plant will default to 28 days — which may not be what the structural engineer intended.
🌊
Treating compressive strength as the only durability parameter. PSI/MPa tells you one thing: how hard the concrete is after 28 days. It says nothing about permeability, sulfate resistance, alkali-silica reactivity risk, or chloride penetration resistance — all of which govern long-term durability in aggressive environments. For marine, wastewater, or freeze-thaw exposed concrete, supplement f'c with a w/cm (water-to-cementitious-materials ratio) limit and specify air entrainment as separate requirements.

Frequently Asked Questions

Multiply the PSI value by 0.00689476 to get MPa. For example, 4,000 PSI × 0.00689476 = 27.58 MPa, which rounds to 27.6 MPa. For quick mental math on a jobsite, use the approximation: divide PSI by 145. So 4,000 ÷ 145 = 27.6 MPa. The exact factor is needed for structural calculations; the approximation is fine for verbal communication and rough checks.
3,000 PSI concrete equals approximately 20.7 MPa (exactly: 3,000 × 0.00689476 = 20.68 MPa). In the European EN 206 classification system, the closest equivalent is C20/25, which specifies a 20 MPa characteristic cylinder strength and 25 MPa characteristic cube strength. This grade is commonly used for sidewalks, residential patios, and lightly loaded footings.
4,000 PSI concrete equals 27.58 MPa, typically rounded to 27.6 MPa for specification purposes. In EN 206 terms, it falls within the C25/30 class. This is the most widely specified strength for commercial slabs-on-grade, structural walls, and general-purpose structural concrete in the United States. It's also the minimum many structural engineers specify for any element exposed to freezing and thawing conditions.
PSI (pounds per square inch) and MPa (megapascals) are both units of pressure used to express concrete compressive strength. They measure exactly the same thing — the force per unit area the concrete can resist before failing in compression. The difference is purely the unit system: PSI is the imperial unit used in the United States and some parts of Canada, while MPa (equivalent to N/mm²) is the SI unit used everywhere else. 1 MPa = 145.04 PSI. Neither is more accurate — they are exact conversions of each other.
Yes, 1 MPa is exactly equal to 1 N/mm². Both expressions are commonly used in structural engineering, and you will see them used interchangeably on drawings and specifications. MPa (megapascal) is the SI unit name; N/mm² (newtons per square millimeter) is the equivalent derived expression. On European and Australian structural drawings, concrete compressive strength is almost always written in MPa or N/mm² — they mean identical things.
C25/30 is a European EN 206 concrete strength class. The "C" stands for concrete, "25" is the characteristic compressive strength in MPa measured on a 150 mm diameter × 300 mm high cylinder (tested per EN 12390-3), and "30" is the characteristic compressive strength measured on a 150 mm cube. The cylinder value is always lower because the geometry of a cylinder creates more stress concentration in the test. The C25/30 class is roughly equivalent to a US 3,600–4,000 PSI specification, depending on whether you match cylinder or cube strength.
5,000 PSI equals 34.47 MPa, typically rounded to 34.5 MPa. In EN 206 terms, this is closest to C32/40. This is considered high-strength concrete in residential and light commercial contexts, though it is standard for bridge decks, parking structures, precast elements, and any structure subject to aggressive environmental exposure. Above 6,000 PSI (41.4 MPa), concrete is generally classified as high-strength concrete (HSC) and requires a specialist mix design from the batch plant.
ACI 318 (American Concrete Institute) has used PSI since its earliest editions because the United States never fully adopted the SI (metric) system in construction. ACI 318M is the metric edition — it uses MPa — but the imperial ACI 318 remains the dominant standard on US projects. Eurocode 2 and EN 206 use MPa because most of the world adopted SI units decades ago. There is no technical advantage to either unit — they are exact conversions — but mixing them up on a project without explicit conversion is a recognized source of specification errors.
ACI 318-19 sets a minimum f'c of 2,500 PSI (17.2 MPa) for structural concrete in most cases. However, the code sets higher minimums for specific conditions: 3,000 PSI for structures in moderate exposure conditions, and 3,500–4,000 PSI for severe freeze-thaw exposure (Exposure Class F1 and F2). Additionally, ACI 318 Section 19.3.3 requires a minimum of 3,000 PSI for prestressed concrete and 4,000 PSI for some seismic applications. The code's absolute minimum of 2,500 PSI is rarely appropriate for any real structural application.
Multiply kgf/cm² by 0.0980665 to get MPa (or divide by 10.197). For example, 300 kgf/cm² × 0.0980665 = 29.4 MPa (roughly 4,270 PSI). The kgf/cm² unit is still common in older Latin American, Japanese, and South Korean structural drawings and is sometimes used in mix design submittals from those regions. The approximate shorthand is: 1 kgf/cm² ≈ 0.098 MPa ≈ 14.2 PSI. This calculator accepts kgf/cm² as an input unit — select it from the dropdown.