30 HOW
x36 30x36=1,080 because whats 6x0? ZERO! 6x3?
____________ Eighteen! When your done with that you drop
180 a zero down to show that you have used it
+ 900 and you keep going 3x0? ZERO! 3x3? Nine of
____________ course. So you got 180 and 900 add it all
1080 together and get......... 1080!
Taaa Daahh!
To convert centimeters to inches, you can use the conversion factor of 1 inch being approximately 2.54 centimeters. Therefore, 30 cm is about 11.81 inches, and 36 cm is about 14.17 inches. So, 30x36 cm is approximately 11.81 inches by 14.17 inches.
The best rule of thumb I have found is: Length X Width / 144 * 288 = Max. CFM I have used this formula to size many HVAC systems. It has always worked. For example, a 5 ton unit should have a 30x36 grille(2-18X30 filters). (30x36)/144*288=2160 max cfm. Return Air should be sized at 200 square inches per ton according to AirMate and other filter grille manufacturers to achieve 2.0 static pressure. The Return Air Duct should have an unobstructed 6 square inches per 1000 BTU of cooling.