Convert Atmosphere to Megapascal (atm → MPa)

Converting atmospheres to megapascals is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.

1. 1
   Take your value in atmospheres

   Start with the number of atmospheres (atm) you want to convert.
2. 2
   Multiply by 0.101325

   The conversion factor from atm to MPa is 0.101325. Multiply your value by this number.
3. 3
   Read the result in megapascals

   The result is your value in megapascals (MPa).

Multiply the value in atmospheres by 0.101325. For the reverse direction, multiply by 9.869233.

• ✓1 atm = 101,325 Pa = 1.01325 bar = 14.696 psi.
• ✓Note: atm ≠ bar. Close but not identical.
• ✓Modern SI prefers pascals; atm is a legacy reference.

• ✗Using 1 atm = 1 bar exactly — off by 1.3%.
• ✗Confusing standard atm with technical atmosphere (98,066.5 Pa) or atmosphere-absolute in diving.
• ✗Applying 1 atm outside sea level without correction.

What is the Atmosphere?

The atmosphere equals exactly 101,325 pascals (the average atmospheric pressure at sea level, latitude 45°) and is a reference unit in chemistry, diving, and engineering. Defined for scientific convenience to represent 'standard atmospheric pressure,' it is widely used in chemistry (gas laws, reaction conditions), aviation (cabin pressure relative to ambient), and scuba diving (depth pressure: every 10 m of seawater adds about 1 atm). Standard reference conditions in chemistry often specify 1 atm and 25°C. The atmosphere relates to the pascal (101,325 Pa = 1 atm), the kilopascal (101.325 kPa = 1 atm), the bar (1.01325 bar = 1 atm), the psi (14.696 psi = 1 atm), the torr (760 torr = 1 atm), and the meter of seawater (10.33 mH₂O = 1 atm). The 'technical atmosphere' (1 at = 98.066 kPa = 1 kgf/cm²) is a slightly different historical unit no longer in use.

• Chemistry standard conditions
• Aviation cockpit pressurisation references
• Pressure tank and vessel ratings

What is the Megapascal?

The megapascal equals 1,000,000 pascals (or 10 bar) and is the engineering high-pressure unit used in hydraulics, materials testing, and construction. Concrete compressive strength is rated in MPa (typical residential concrete is 20–35 MPa, structural concrete 35–70 MPa, high-strength up to 140 MPa), and steel yield strengths are 250–700 MPa for structural grades. Hydraulic systems operate at 10–70 MPa, and high-pressure-water-jet cutting reaches 400 MPa. The megapascal is dimensionally identical to N/mm² (newtons per square millimeter), making it natural for engineering calculations involving small areas. Earth's mantle pressure reaches gigapascals (1 GPa = 1,000 MPa). The MPa relates to the pascal (10⁶ Pa = 1 MPa), the bar (10 bar = 1 MPa), the psi (1 MPa ≈ 145.04 psi), and the atmosphere (1 MPa ≈ 9.87 atm). It is the standard unit in modern engineering specifications worldwide.

• Hydraulic system pressures
• Concrete and steel strength specifications
• High-pressure industrial processes