Atmospheres to Newtons per Square Millimetre (atm to N/mm2)

Formula

N/mm² = atm × 0.101325

or N/mm² = atm ÷ 9.86923266716

Derivation from SI units:

• 1 atm = 101 325 Pa (exact, by definition)
• 1 N/mm² = 1 N ÷ 10⁻⁶ m² = 10⁶ Pa = 1 MPa
• 1 atm = 101325 Pa ÷ 1000000 Pa per N/mm² = 0.101325 N/mm²

Both units are defined exactly, so the factor is exact. Atmosphere definition: atmosphere; Newton per Square Millimetre definition: newton per square millimetre.

Worked examples

1. A reading of 1.5 atm converts to 0.1519875 N/mm².
   1.5 atm × 0.101325 = 0.1519875 N/mm²
2. A value of 10 atm is 1.01325 N/mm².
   10 atm × 0.101325 = 1.01325 N/mm²

Where it's used

Atmospheres are used for chemistry and gas laws (STP and NTP conditions), while newtons per square millimetre appear in steel yield and tensile strength (S355: 355 N/mm²). Both measure pressure, stress and differential pressure (force per unit area), so the conversion is a fixed factor.

Atmosphere to other pressure units

Frequently asked questions

Sources

• Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "atmosphere, standard (atm)".
• The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures , Table 4, coherent derived units with special names.

Last reviewed: 2026-10-15. Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.