Pressure Dewpoint Calculator

By October 13, 2023News

Dew Point Calculations and Conversions

To support your dew point calculations and conversions, we offer two types of pressure dewpoint calculator for trace moisture measurement. We provide a handy, pressure dewpoint calculator with all of our dewpoint meters, trace moisture analysers and hygrometers. Alternatively, if you prefer, you can use our online version. Both calculators bring together many different measurement units and enable dew point calculations and conversions for moisture levels at different pressures.

A quick and simple explanation for dew point is: it is the temperature at which air must cool for the water vapour within to condense into dew or frost. We refer to temperatures above 0 °C as dew point and temperatures below 0 °C as frost point. Additionally, we express dew point in degrees Celsius (°C) or degrees Fahrenheit (°F).

Handy, Portable Pressure Dewpoint Calculator

How to AutoCal the SADP dew point meter
Shaw pressure dew point calculator ,measure and convert trace moisture content measurements

This calculator is extremely handy and perfect for onsite visits and spot check reading conversions. It stores easily in the carrying case alongside your portable dew point meter and is always ready to use, even in hazardous areas.

One side of the pressure dewpoint calculator displays any dew point temperature at any given pressure. You can calculate and/or convert this dew point temperature to the equivalent dew point temperature at any other pressure and view trace moisture content in parts per million (ppm(V)).

On the reverse of the calculator is a table displaying easy conversions for dew point temperature. Use this side to convert your measurement units to:

  • °C – degrees Celsius
  • °F – degrees Fahrenheit
  • g/m³ – equivalent moisture levels in mg/water per litre
  • lb/MMSCF – lb/water per million cubic feet
  • ppm(V) – parts per million water vapour by volume
  • pascals – water vapour pressure

PLEASE NOTE: All conversions from our pressure dewpoint calculator are based on ideal gas behaviour.

Step-by-Step Guide – How to Use Your Pressure Dewpoint Calculator

Follow our step-by-step guide or watch the video tutorial below.

Shaw Moisture Meters pressure dewpoint calculator

The pressure dewpoint calculator consists of three parts: A is the base wheel for trace moisture content, B is the centre wheel for pressure input and C is the alignment arrow.

Dewpoint calculator, pressure dew point calculator, Shaw Moisture Meters, dew-point degrees Celsius


After taking a reading (we used the SADP dewpoint meter), rotate the centre wheel [B] to match the dew point shown on the instrument. For this example, we will use -40 °C. We designed the SADP portable dewpoint meter to work at atmospheric pressure.

Pressure dewpoint calculator, dew point meter, shaw moisture meters


Move the alignment arrow [C] to line up with the Atmospheric Pressure indicator.

This displays the equivalent moisture content on the base wheel in parts per million (ppm(V))

Select units and pressure for calculating dew point with Shaw Moisture Meters dew point calculator


Hold the alignment arrow [C] and the moisture content value in a fixed position. Now rotate the centre wheel [B] to change the pressure.

calculate trace moisture measurement, Shaw Moisture Meters dew point


For this example, we have rotated the wheel anti-clockwise to 10 bar(A).

dewpoint calculation for process gases and dry compressed air


The pressure dew point in °C is now visible on the calculator, indicating a value slightly over -17.5 °C dew point.

SHAW dewpoint calculator conversion units


Convert your new reading to another measurement value by using the reverse of the SHAW pressure dewpoint calculator.

convert dew point measurement Shaw Moisture Meters


Rotate the alignment arrow to your °C result from STEP 5, e.g., -17.5 °C to view calculable conversions in the following units: °F, g/m³, lb/MMSCF, ppm(V) and ppm(w).

Taking a Spot Check Reading

If you need any further information or help taking a reading with your dewpoint meter please contact us or visit the tutorial Taking a Spot Check Reading.

If you have any questions about our dew point calculators, need any further advice or can’t find what you’re looking for, please contact: +44 (0) 1274 733582, or fill out the form on our Contact page.

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Written and issued by Shaw Moisture Meters