The mixing ratio of air calculator works out saturated vapor pressure, saturation mixing ratio and actual vapor pressure from air temperature, dew point, station pressure and one way. Enter what you have and the relationship is applied straight away, so you get the answer without working through the algebra yourself.
What Is the Mixing Ratio of Air Calculator?
This mixing ratio of air calculator is for the kind of problem where you know the physical quantities but not the number you need. It turns air temperature, dew point, station pressure and one way into saturated vapor pressure, saturation mixing ratio and actual vapor pressure.
Physics calculations go wrong in predictable ways, usually through mixing units or dropping a digit. Work through the result one step at a time and check that the figures are the size you would expect at each stage.
How the Mixing Ratio of Air Physics Works
The relationship is applied step by step, and each step is a standard piece of physics rather than a single opaque formula. That means you can check the intermediate values against what the theory predicts, which is usually faster than checking only the final answer.
Keep every value in the same unit system throughout the calculation. Mixing metres and feet part way through is the single most common reason a correct formula gives a wrong answer.
Units, Assumptions and the Limits of the Model
The calculation assumes ideal conditions: no air resistance, no heat loss, and dimensions that do not change while you work. Those assumptions are reasonable for most classroom and engineering estimates, and unreasonable for anything more precise.
Where a value is a rate, it has to be quoted for the same period as everything else. A per-hour figure cannot be combined with a per-day figure without converting one of them first.
A Worked Example
Working through an example, with air temperature set to 10, dew point set to 5, station pressure set to 2, the calculator returns actual mixing ratio of -807.06, and saturation mixing ratio of -743.1, and relative humidity of 1.09. Substitute your own figures and the same steps produce the same kind of answer.
Frequently Asked Questions
What do I need to work out saturated vapor pressure?
Enter air temperature, dew point, station pressure and one way. The calculator then works through the relationship and reports saturated vapor pressure, saturation mixing ratio and actual vapor pressure.
What does the mixing ratio of air actually calculate?
It takes air temperature, dew point, station pressure and one way and converts them into saturated vapor pressure, saturation mixing ratio and actual vapor pressure using the standard relationship for this problem. Each step is applied in turn, so every output is traceable back to the numbers you typed in.
How should I enter air temperature?
Use the value you actually have, in the unit shown next to the field. Enter every value in the same unit system. The calculator assumes the figures you supply are consistent, so it cannot correct a mistake that happens before the calculation starts.
Is the answer exact?
It is as exact as the formula and the inputs allow. The method itself is the standard one for this problem, so the only sources of error are the figures you enter and the precision you ask for.
Do I have to fill in every field?
Only the fields a particular result depends on. If you leave one blank, the results that need it simply show a note instead of a number, and everything else still works.