Technical Atmospheres to Bars (at to bar)

1 technical atmosphere equals 0.980665 bars exactly.

How to convert technical atmospheres to bars

To convert technical atmospheres to bars, multiply the number of technical atmospheres by 0.980665. This factor is exact. To go the other way, multiply bars by 1.019716213 (rounded).

bars = technical atmospheres × 0.980665

Example: 10 technical atmospheres = 9.80665 bars.

About these units

Technical Atmosphere (at)

CGS & old metricHistorical unit (no longer in standard use)

Exactly 98,066.5 pascals: one kilogram-force per square centimeter. Still seen on gauges in older equipment.

Pressure given as kilograms-force per square centimeter is the technical atmosphere, symbol at. It is fixed by arithmetic rather than by any air measurement: one kilogram-force is 9.80665 newtons and a square centimeter is one ten-thousandth of a square meter, so the unit is exactly 98,066.5 pascals, or 98.0665 kilopascals. Shop-floor shorthand includes kg/cm2, kp/cm2 and, in some older publications, ksc.

It is close to, but not the same as, other familiar pressures. It is about 0.981 bar, roughly 2 percent below a bar, and about 0.9678 of a standard atmosphere. In pounds per square inch it comes to about 14.22. The unit is deprecated and outside SI, yet it lingers because older pressure gauges and equipment, including Soviet-made instruments, are still in service with dials marked in kgf/cm2. NIST conversion tables list it with an exact factor to the pascal.

1 technical atmosphere = 98,066.5 pascals (exactly).

Sources: Wikipedia: Technical atmosphere; NIST SP 811, Appendix B.8 conversion factors; Wikipedia: Kilogram-force

Bar (bar)

Metric (SI)Current unit

Exactly 100,000 pascals, close to atmospheric pressure at sea level. Used for tire pressure, diving and industrial gauges.

Bar began as a name that meant different things to different people. It comes from the Ancient Greek baros, weight, and from 1793 to 1795 an early metric system used bar for a unit of mass equal to the modern tonne. The pressure bar was introduced by the Norwegian meteorologist Vilhelm Bjerknes, a founder of modern weather forecasting, who defined it as one megadyne per square centimeter. Some earlier writers had used bar for one dyne per square centimeter, a source of confusion.

The bar is a metric unit but not part of the SI, and its official symbol is simply bar, since the old b clashes with the barn and the bit. It has been legally recognized in EU countries since 2004, although NIST deprecates it except for limited use in meteorology.

Its size is handy because 1 bar is slightly less than average sea-level pressure, which is about 1.013 bar. In scuba diving every 10 meters of seawater adds about 1 bar and a full standard tank holds about 200 bar. Tire pressure and turbocharger boost are often quoted in bar outside the US.

1 bar = 100,000 pascals (exactly).

Sources: Wikipedia: Bar (unit); Wikipedia: Atmospheric pressure

Related conversions

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