ATM Pressure Conversion Calculator
Convert standard atmospheres into bar, pounds per square inch, pascals, kilopascals, and millimeters of mercury with one synchronized input.
Input
Converted pressure
Conversion details
| Unit | Symbol | Conversion factor from atm | Current value |
|---|---|---|---|
| Standard atmosphere | atm | 1 | 1 |
| Bar | bar | 1.01325 | 1.01325 |
| Pounds per square inch | psi | 14.6959487755 | 14.69595 |
| Pascal | Pa | 101325 | 101,325 |
| Kilopascal | kPa | 101.325 | 101.325 |
| Millimeter of mercury | mmHg | 760 | 760 |
| Torr | Torr | 760 | 760 |
How to use the ATM pressure conversion calculator
What this calculator does
This calculator converts a pressure expressed in standard atmospheres into several widely used pressure units. It is useful when a specification, laboratory note, weather reference, tire or vessel document, or engineering calculation uses a different unit from the one you need. The conversion is an exact linear unit conversion based on the defined standard atmosphere. It does not estimate local weather pressure, altitude, gauge pressure, fluid head, or the operating safety of pressure equipment.
When to use it
Use it to translate a laboratory pressure stated in atmospheres into SI pascals, compare an equipment rating stated in bar with a value in atm, read a pressure value in psi for a U.S.-formatted document, or check a familiar sea-level reference in kilopascals or millimeters of mercury. For formal scientific work, the BIPM SI Brochure explains the SI system and the pascal as the coherent pressure unit.
How to calculate
- The calculator opens with a demonstration value of 1 atm. Its results are already calculated, and the example Excel workbook is immediately available.
- Replace the value in Pressure in atmospheres with the pressure you want to convert. Use ordinary decimal notation, such as 0.85, 1, or 2.5. A period is the accepted decimal separator.
- Read the live result cards and the conversion table. Every displayed unit is driven by the same atmosphere input, so the values remain synchronized.
- Select Download Excel to generate a fresh workbook from the current validated value. The workbook includes Summary and Inputs sheets plus the complete conversion table.
- Select Reset to clear the demonstration and all calculated content. Reset may disable Download Excel until a complete valid atmosphere value is entered again.
Input guide
Pressure in atmospheres is the only input. It is required, measured in standard atmospheres, and accepts a finite nonnegative decimal. A realistic example is 1.2 atm. Increasing the value increases every converted result in direct proportion; halving the input halves every output. Do not enter unit letters inside the field, do not use scientific notation, and do not use a comma as a decimal separator. A blank, negative, malformed, or excessively large value is rejected rather than silently changed.
Output guide
Pressure in pascals is the primary result and uses the SI unit Pa. Pressure in bar, Pressure in pounds per square inch, Pressure in kilopascals, Pressure in millimeters of mercury, and Pressure in torr are equivalent representations of the same pressure. Atmospheres entered repeats the validated source value for traceability. The summary pills show the current bar and psi values. Each table row identifies the unit, symbol, factor from atm, and current converted value. Zero means zero absolute pressure in this purely mathematical conversion; it should not be confused with zero gauge pressure. These outputs are exact unit identities subject only to displayed decimal rounding, not recommendations or physical measurements.
Worked example
The startup example uses 1 atm. The calculator multiplies that value by the defined factors: 1 × 101,325 = 101,325 Pa; 1 × 1.01325 = 1.01325 bar; and 1 × 14.6959487755 = 14.69595 psi after display rounding. It also shows 101.325 kPa, 760 mmHg, and 760 Torr. Those same canonical values populate the first-open results, the detail table, and the downloadable workbook.
How the conversion works
A standard atmosphere is defined as exactly 101,325 pascals. Because the units describe the same physical dimension, the conversion uses multiplication by a constant rather than a nonlinear formula. The pascal itself is one newton per square meter, as described in the BIPM overview of the International System of Units.
bar factor: 1.01325 · psi factor: 14.6959487755 · Pa factor: 101,325 · kPa factor: 101.325 · mmHg and Torr factor: 760
The linear relationship means conversion preserves ratios. Two atmospheres are exactly twice the pressure of one atmosphere in every listed unit. Rounding affects only what is printed on screen or formatted in Excel; the canonical model retains full numeric precision for the conversion factors used here.
Absolute pressure, gauge pressure, and context
The atmosphere unit normally represents absolute pressure. Many instruments, however, report gauge pressure relative to the surrounding air. A gauge reading of zero therefore does not usually mean zero absolute pressure. Before converting a specification, confirm whether the source value is absolute or gauge pressure. The NIST guidance on SI pressure units provides additional context for expressing pressure in pascals and related SI multiples.
Local atmospheric pressure also changes with altitude and weather. This calculator does not model those changes; it only converts a supplied number. For meteorological observations, use an actual measured or officially reported pressure and then convert that value. Do not assume every location or day is exactly one standard atmosphere.