Free · Unit conversions

Mercury, Water Column & Atmosphere Comparison

Mercury, Water Column & Atmosphere Comparison with editable units, inverse inputs and a worked example.

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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

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Formula and method

A 760 mmHg pressure converts to about 1.000000142 standard atmospheres under this mercury convention. The optional mmH₂O unit uses a different conventional density.

Standard atmospheres = mmHg × 133.322387415 ÷ 101,325; conventional mmH₂O = 9.80665 Pa

Worked example

Enter these known values and leave the other values blank.

Pressure A
760 mmHg
Pressure B
1 atm

Assumptions and limitations

  • All fields express the same pressure quantity. Unit conversion preserves its reference: absolute, gauge or differential. It does not add or subtract local atmospheric pressure.
  • Zero and signed values are supported for mathematical or differential-pressure comparisons. Negative absolute pressure is outside the physical meaning of these units.
  • Standard atmosphere means exactly 101,325 Pa; technical atmosphere means 98,066.5 Pa. PSI and force-per-area units use standard gravity, 9.80665 m/s², with international length and mass definitions.
  • The retained mmHg convention is 133.322387415 Pa, distinct from a torr (101,325/760 Pa). Optional inHg retains the captured approximate 3,386.39 Pa factor. These manometer conversions are not a temperature-dependent liquid-column simulation.
  • Where present, water-column units are conventional: 9.80665 Pa per mmH₂O and 98.0665 Pa per cmH₂O. A metric tonne-force is 1,000 kg-force. Display rounding does not establish measurement accuracy.

Common questions

What relationship does this comparison use?

A 760 mmHg pressure converts to about 1.000000142 standard atmospheres under this mercury convention. The optional mmH₂O unit uses a different conventional density.

Does changing units turn gauge pressure into absolute pressure?

No. This conversion keeps the same pressure reference. Gauge-to-absolute conversion requires adding the applicable ambient pressure separately.

Can I calculate in the opposite direction?

Yes. Enter a known value in any field and leave the others blank. Read the selected unit beside each value, since every comparison field can use a different unit.

References

Pounds-force per square inch use the exact international pound and inch with standard gravity, replacing the rounded captured factor. One technical atmosphere is exactly one kilogram-force per square centimeter under standard gravity. Pounds-force per square foot use the exact international pound and foot with standard gravity. The tonnes-force pressure option uses metric tonnes and standard gravity, with one tonne-force per square meter equal to 9806.65 pascals. Conventional water-column units use standard gravity and the conventional 1000 kg/m³ water density; they do not simulate a physical column at a measured temperature.

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