Standard atmospheres to Bar Calculator

Direct answer

Multiply the entered standard atmospheres value by 1.01325 to express it in bar (bar). This converts standard atmosphere (atm) to bar (bar) within the documented pressure family.

Variables and formula

• Standard atmospheres (atm): the source value measured in standard atmosphere.
• Bar (bar): the same quantity expressed in bar.
• Conversion factor: 1.01325 bar per standard atmosphere.

Bar = Standard atmospheres × 1.01325

The generator emits numeric factors with at most 15 significant digits. Calculator results keep up to 10 significant digits for display; this formatting does not increase the precision of the measurement.

Unit definitions and named variants

Source unit: standard atmosphere (atm). The standard atmosphere is defined as exactly 101,325 Pa. Named variant used: Standard atmosphere (atm); not technical atmosphere (at) or a measured local atmospheric pressure. Reference: National Institute of Standards and Technology: NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically.

Target unit: bar (bar). The bar is a non-SI pressure unit defined as 0.1 MPa or exactly 100,000 Pa. Named variant used: Pressure unit bar; not the unrelated typographic or musical word. Reference: Bureau International des Poids et Mesures: The International System of Units (SI), 9th edition, version 4.01; National Institute of Standards and Technology: NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically.

The atm-to-bar direction remains inside the pressure quantity; it changes the unit label and numerical scale, not the kind of quantity being measured.

Relationship and precision

The named unit relationships are defined or exact, so the conversion is exact before display rounding and source-measurement uncertainty.

• atm relationship: The relationship to the pascal is exact.
• bar relationship: The relationship to the pascal is exact.

To audit the factor through the family base unit, divide the raw dataset factors 101325 by 100000. The generator emits that quotient once at 15 significant digits as the canonical direct factor 1.01325; runtime calculations do not divide the already-emitted base factors again.

Reproducible example

For 10 standard atmospheres, 10 × 1.01325 = 10.1325 bar. Repeating the same multiplication with the stated factor reproduces the displayed conversion before interface rounding.

Directional scale check

Because one standard atmosphere contains 1.01325 bar, the target number is larger than the source number for every positive input. Zero maps to zero, while negative inputs are rejected because this family models non-negative magnitudes.

Interpretation

Read the result as bar, not standard atmospheres. A value entered as atm leaves the calculator labelled bar; this directional distinction matters even when the two units describe the same pressure quantity.

Assumptions and limitations

• Only non-negative pressure magnitudes are accepted; negative gauge readings require a signed, reference-aware model.
• Input and output must refer to the same pressure reference and measurement conditions; a unit conversion alone cannot change the reference datum.
• Psi means pound-force per square inch (lbf/in²) using standard gravity, not pound-mass per square inch.

Common mistakes

• The technical atmosphere (at) is based on kilogram-force per square centimeter and differs from atm.
• One bar is not exactly one standard atmosphere; 1 atm = 1.01325 bar.

Continue within the Pressure family

See the Pressure conversion hub for its five-unit reference table and all 20 directed routes.

• Reverse the direction: Bar to Standard atmospheres
• Compare another pressure route: Standard atmospheres to Pascals
• Compare another pressure route: Standard atmospheres to Kilopascals
• Compare another pressure route: Standard atmospheres to Pounds-force per square inch
• Compare another pressure route: Bar to Pascals

Assumptions

• The entered value uses standard atmospheres exactly as labelled.
• Only non-negative pressure magnitudes are accepted; negative gauge readings require a signed, reference-aware model.
• Rounding and measurement uncertainty remain the user's responsibility.

Sources and methodology

CalcMotive publishes the formula and assumptions so you can decide whether the estimate fits your use case. See our methodology standards.

• The International System of Units (SI), 9th edition, version 4.01; Bureau International des Poids et Mesures; accessed Aug 7, 2026
• NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically; National Institute of Standards and Technology; accessed Aug 7, 2026