The calculator is used to test your eyesight and recognize the difference in color shades. After clicking on the first lighter field, the calculator will change colors and the countdown will begin. Each test takes 15 seconds. Search for a lighter field and click on it. Each subsequent test is more difficult. The test will be aborted if you do not give the correct answer within 15 seconds or if you make a wrong choice three times.

The calculator is used to calculate the ventilation capacity in an attic or loft for the minimum, normal and extreme thermal conditions of the environment depending on the area and height of the room and the roof pitch. The fan removes warm air from the room and should be mounted at the highest possible point for the best efficiency.

With this calculator you will calculate the average absolute deviation, or mean absolute deviation (MAD), of a data set is the average of the absolute deviations from a central point.