Dehumidifier Calculation in Excel


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This excel sheet calculates the dehumidifier capacity for reducing the humidity in a warehouse, cold room, warehouse, industries etc.

How to calculate the capacity of dehumidifier?free-download-dehumidifier-calculation-excel-sheet

In layman’s language, dehumidification process is the removal of water from the surrounding air. Bringing down the humidity levels means reducing the moisture content in the air.

So the capacity of a dehumidifier is defined as its capacity to remove the water content. eg. a dehumidifier with a capacity of 24 litres per day means it can remove 24 litres of water in a day. So effectively, moisture content totalling 24 litres can be removed in a day by this particular dehumidifier.

Steps for calculating dehumidification capacity and selecting the right dehumidifier

For any applications covering residential, commercial or industrial, you can calculate the dehumidification capacity and select a suitable dehumidifier as per the following steps:

  1. Measure the present temperature (°C or °F) and present relative humidity (%RH).
  2. Decide the humidity level you want to achieve and maintain (%RH).
  3. Measure the size of the room or warehouse. Length, Width & Height are required. Calculate the volume of the room by multiplying Length, Width and Height.
  4. If you have an existing HVAC system, check the fresh air intake percentage.
  5. Convert the present relative humidity into absolute humidity.
  6. Convert the desired relative humidity into absolute humidity.
  7. Find out the difference between values of Sl. nos. 5 & 6 above. This is the volume of moisture content to be removed from one cubic meter.
  8. Multiply the result obtained in step 7 by the total volume of the room.
  9. This gives the total required capacity of the dehumidifier in litres per hour at the measured room temperature. Now you can select the right dehumidifier matching the capacity.
  10. If your room temperature is above 10°C, you may go for a condensation dehumidifier. If the room temperature is below 10°C, you may choose a desiccant dehumidifier.
  11. Please note that the capacity of a dehumidifier varies as per the temperature. Hence never select a dehumidifier based on its maximum specified capacity. Please look for the performance chart of the dehumidifier. This will indicate a performance graph at different temperatures. You may select the right capacity at your room temperature.

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Details required to calculate de-humidification capacity

In order to calculate the required capacity of a dehumidifier, you need to collect the following details:

  1. The size of the room in cubic meters.
  2. Present temperature of the area, preferably the maximum recorded temperature reading.
  3. Present or maximum humidity levels without a dehumidifier in %RH (You can use a data logger or hygro meter to find out the same. Data logger will record the data over a time. Hygrometer will not record the data, but only will display on the screen.)
  4. Required humidity level to which you want to reduce the humidity levels in %RH.
request-quote-vackerMethod for calculating de-humidification capacity

All the normal humidity measuring instruments will indicate the humidity levels in %RH. This has to be converted to absolute humidity which means the amount of moisture per cubic meter. Absolute humidity will be automatically calculated in the excel sheet for Sl. no. 3 & 4 defined above.

The difference between the absolute humidity of 3&4 above gives the moisture content to be removed from 1 cubic meter.

Multiply  this result by the volume of the room which will provide the total volume of the water to be removed from the room to bring the humidity down to the desired levels.

How to calculate the capacity of dehumidifier in Excel?

The above entire calculation is formulated in this free excel sheet. You need to enter only the input values as above and the results are automatically generated.

Example of calculation of de-humidification capacity

The above calculation is explained in the following example.

We assume the following values:free-download-dehumidifier-calculation-excel-sheet

  1. The present temperature of the room is 30°C.
  2. The present humidity of the room is 70% RH.
  3. Desired humidity of the room is 50% RH.
  4. Room size is 5 mtr (L) x 5 mtr (W) x 3 mtr (H).

From the above example we can calculate the following:

  1. Absolute humidity corresponding to 70% RH is equal to 21.23149 gram/cubic meter.
  2. Absolute humidity corresponding to 50% RH is equal to 15.16535 gram/cubic meter.
  3.  The Volume of the room is equal to 5x5x3 is equal to 75 cubic meters.

The difference of 1&2 above is 6.07 gram/cubic meter. This means that 20 gram of water has to be removed from each cubic meter to achieve 50%RH.

Hence for a volume of 75 cubic meters, required dehumidification capacity is 455 gram per hour ( 6.07 x 75 ).

This is equal to 0.455 kilograms per hour or 0.455 litres per hour. Calculating values per day, this amounts to 10.92 kg per day or 10.92 litres per day.

Hence you can select a dehumidifier with a capacity of 10.92 litres per day to meet your requirement. Among our various models, you can select the nearest model  TTK 40E which has a capacity of 12 litres per day at 30°C.

How to calculate which dehumidifier to use?
Also, you can use our online calculator for dehumidifier capacity calculation. Upon calculating the required capacity you can use the selection chart on the same page to select a suitable model. For bigger rooms,  it is better to select multiple smaller models instead of one big model. This is to improve the air circulation. eg. If you provide one big dehumidifier of 300 liters per day, in one location of a warehouse it will not provide enough air circulation around the warehouse. It will be better to provide 4  dehumidifiers each of 75 liters per day.
How to calculate the dehumidifier capacity in pint/day?

The above excel sheet is providing the results in litres per day. If you want to convert the capacity into pints per day, please use proper conversion. For conversion into US pints, you may use the multiplication factor of 2.11337642 to derive pint per day from litre per day.

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19 comments on “Dehumidifier Calculation in Excel
  1. I am looking for dehumidification equipment for accommodation on an offshore installation. The equipment should be capable of handling the humidity over 3 floors, individual rooms and corridors along with control rooms etc, do you have a technical person i could speak to?

  2. Nader says:

    Dear Sir
    I am enquiring about a dehumidifier of 300 to 400 liter per day (or few smaller ones)that I can use at my home. Please, advise me to the right model and it’s price.

    Thank you very much
    Nader Shabani

    • Vacker says:

      300 to 400 liter per day will be very huge for a room. IF you are planning a duct system for the whole house, probably you will require this much capacity. Did you calculate using our calculator? What was result you obtained?

  3. munawar says:

    i want to calculate dehumidifier size for swimming pool

  4. kevins says:

    That is a good calculator. So this capacity calculation is the first step for selecting a dehumidifier? I do not know current humidity in my room. How to proceed?

  5. loay says:

    thanks very much for the calculation sheet

  6. Traek saeed says:

    thanks very much for the calculation sheet

  7. We require dehumidifier for blast chamber. Size 13meter*14meter*22meter. Temp. required 25Celcius. Outside temp. is 32 celcius.

  8. I want to buy 2 sets of dehumidifiers please.

  9. Washington Wiah Stevens says:

    Thanks very much for the calculation sheet.

  10. gaurav says:

    I have a lab size of 38’x18’x12′. The RH at present is around 70%. I need it to be around 45%. What capacity of dehumidifier I need and please suggest your model no.

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