How much CFM do I need for my Kitchen?
Before starting, let’s understand what is CFM? CFM stands for Cubic Feet per Minute. CFM measures the volume of air, in cubic feet, for each minute it moves. CFM is a good measure of how much air goes through the blower via your Range hood. When deciding how much CFM you need for your range, the first thing you need to take into consideration is the type of range and output you have.
For an electric range, multiply the width of your stove in inches by 10 to get the minimum CFM for your Range Hood. For example, if your cooktop is 36 inches, you’ll want at least 360 CFM .
Gas ranges, grills and barbecues are a bit different because they produce a lot more heat and fumes. The amount of heat emitted from a gas cooktop is measured in British Thermal Units or BTU. If your owner’s manual doesn’t tell you the total BTU of your cooktop, you can find it by adding the BTU of each burner together, then dividing that number by 100. For example, if you have two burners that each put out 10,000 BTU and two burners that put out 15,000 BTU, your total BTU for your stovetop would be 50,000. 50,000 divided by 100 equals 500. So you’ll want a minimum of 500 CFM for your range hood over your gas stove.
Grills and barbecues have higher BTU than an indoor gas range, but the calculation is the same. Now take the minimum CFM number you just got and you have a decision to make. There’s a quick way and a more precise way to know how many totals CFM you’re going to need for your new hood. We’ll cover them both the quick way, just add 200 CFM to your minimum CFM number you just calculate it and you’re good to go.
If you want to be a little more thorough, don’t just add the extra 200 cfm but follow these next steps instead. Keep your minimum CFM number handy because we’ll use it again shortly. Now we’re going to factor in the size of your kitchen. Determine the volume of your kitchen by multiplying its length, width, and height together. For example, if your kitchen is 18 feet long, 14 feet wide and 9 feet tall. multiply 18×14 by nine and you get 2268 cubic feet. Larger kitchens will need to move more smoke and unwanted air to keep the air clean and harsh cooking odors at bay. As a rule for ventilation, a range hood needs to have the power to exchange your kitchen air 15 times per hour. To get that number, multiply your kitchen cubic feet by the air exchanges. For example, 2268 cubic feet by 15 air exchanges equals 34,020 cubic feet per hour. Now divide that by minutes in an hour. 34,020 cubic feet divided by 60 minutes per hour will give you the CFM needs of your kitchen space. In this example, you’ll want a minimum of 567 CFM . Compare this number to your minimum CFM number that you calculated earlier, circled the larger of the two and let’s move on. We’re nearly done. Then calculate the additional CFM needs of your ductwork. For each foot of ductwork, increase your CFM by one. For each turn in your duct, increase your CFM by 25 and if you use a roof cap, increase your CFM by 40. An example if your ductwork consists of 12 feet of pipe, two turns and a roof cap, you’ll add 12 CFM for the 12 feet of pipe 50 CFM for the two turns and 40 CFM for the roof cap. Now take the CFM number you circled earlier and add your ductwork number to it. In our example, we’ll add 102. 567 plus 102 equals 669 CFM. Once you’ve finished this calculation think about your cooking routine. If you enjoy using your stovetop frequently or do a lot of Asian cooking, frying, barbecuing, boiling or searing, add another 200 CFM to the total you have. In our example we do a lot of searing and frying, so we’re going to add an additional 200 CFM which looks like this.
669 CFM plus 200 equals 889 Total CFM to make shopping for a hood easier, round up to the nearest 100 CFM. So we’ll round up to 900 CFM . And that’s it. That’s the more thorough way to calculate the CFM you’ll need for your new hood. Now all you have to do is find the right range hood for your kitchen.