We’ve tested the best battery-powered leaf blowers and the best gas leaf blowers to see who reigns supreme. During our testing, a discussion came up about why manufacturer CFM specs tend to be pretty far off from reality. It also opened up other questions. One of the most common we come across was the difference between leaf blower MPH vs CFM. Which one is actually more important?
We take a look at each and even throw an additional term into the mix to help you sort it all out.
Table of Contents
Understanding MPH – Miles Per Hour
In the leaf blower MPH vs CFM conversation, miles per hour represent a measurement of airspeed. That seems fairly easy to understand. After all, we’re used to seeing MPH speeds in cars, wind speeds (think hurricanes), and other areas. At its core, MPH tells you how many miles you get when traveling for one hour at a constant rate.
A blower that produces 200 MPH windspeed would push a burst of air 200 miles away in an hour if that burst could maintain its speed. Simple enough.
Air Volume as CFM – Cubic Feet per Minute
Blower CFM, or cubic feet per minute, measures the volume of air leaving the blower. In this case, the impeller creates a vacuum effect, pulling air through itself and pushing it out the other end. The angle, length, and speed of rotation of the blades determine how much air moves through and determines both the speed and volume of air moving. Consider a backpack blower that claims to get 1000 CFM (and let’s assume you actually get it for the sake of the example). That 1,000 CFMs means that the blower moves enough to fill a cube that’s 10 feet high, 10 feet wide, and 10 feet long in 1 minute.
Comparing MPH vs CFM in Leaf Blowers
Airspeed is important because it takes more of it to move heavier objects. Dry grass is one thing. pebbles, mulch, and wet leaves are another. Air volume is important because you need more to move debris in a larger area. But is blower MPH or CFM more important? Consider a couple of examples.
Take a straw and blow air through it at 300 MPH. You’ll make an impressive mess with your glass of milk or make a pretty effective blow-dart gun, but you’ll accomplish very little in your yard. You’re in a low CFM situation, and the airspeed can only affect a small area.
On the other side of the MPH vs CFM coin, let’s say that you can produce 20,000 CFM but only get 15 MPH out of it. You get a nice breeze for a hot day. You and four of your closest friends can stay cool, but you’re only going to be moving the lightest sawdust. The low airspeed means you’re not moving much weight around.
You need a combination of both MPH and CFM to get the job done, but is there a correct balance? Or at least a way to decide how much work a blower accomplishes to compare with others?
Newton Force – A Better Picture Than MPH or CFM
Let’s talk about Newtons. No, we’re not talking about the fig kind, this is all about force. The formal definition says that one Newton equals the force required to accelerate an object with a mass of 1 kilogram 1 meter per second per second. OK, now that we cleared that up, let’s make some sense of it.
Newton force is the number you want to look for when comparing blowers. Because of the way it is tested, it takes the effect of both the blower MPH and CFM to give you one number representing the total amount of force produced. In our head-to-head comparisons, we found cordless blowers producing anywhere from 8 to 17 N (Newtons). Professional backpack blowers produce between 28 and 41 N. With a simple “bigger is better” kind of measurement, it’s much easier to see which blower is more powerful.
However, you can’t just plug CFM and MPH into an equation and get Newtons out. It’s complex and involves temperature, humidity, pressure, and other factors. It’s far easier to simply measure Newtons than calculate them, and it’s something we test and report in our blower reviews. We use a Shimpo meter to measure Newton-Force and it works really well.
Blower MPH vs CFM – The Final Word
Here’s the cool thing: more brands are beginning to include Newton force in their specifications—right alongside blower MPH and CFM numbers. That makes it much easier for you to compare which leaf blower is the best one for your needs.
Now that you have a better understanding of all three parameters, those numbers on the box might mean a little more when you shop and compare products.