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# CFM vs. MPH – The Battle of Numbers

To accurately compare any two or more devices, we often resort to the numbers. We assume that superior technical specifications, or more accurately “the larger“ numbers, are a sign of a better product. Yet when it comes to leaf blowers, this assumption may lead you to a bitter surprise.

## What is CFM and MPH?

The two specifications that characterize a leaf blower’s “ability to blow” are the cubic feet per minute (CFM) and the miles per hour (MPH).

CFM (Cubic feet per minute)

• The unit of volumetric flow. That is the sum of the cubic feet of wind that flow through the nozzle of the leaf blower each minute.

MPH (Miles per hour)

• The unit of velocity (a fancy word for speed) of the wind that is being ejected by the device at any given moment.

At first sight, many of us may be baffled by the necessity for listing both specs. Aren‘t they basically the same thing? No! Moreover, both are needed to characterize the leaf blower’s ability to do its job.

A brief rundown of the leaf blower’s function.

This results in the CFM and MPH.

If you are still confused by the difference between the two, consider the following example.

Imagine that you are blowing out candles on a birthday cake. While you may easily be able to do it in one blow just with your mouth, try doing it with a straw. Two things happen:

Does this mean that velocity is therefore a useless metric? No! In order to actually move the leaves, you need to apply efficient velocity. In fact, the heavier the object, the larger MPH is required to move it.

We can therefore conclude, that:

For further information about air flow, visit https://en.wikipedia.org/wiki/Fluid_dynamics (opens in a new tab).

## Considering the CFM/MPH ratio

The specifics of what we consider a high/low MPH and CFM depend on the size of a device and its intended application, yet we can still draw some general conclusions just based on the ratio of the two metrics alone.

### High CFM/High MPH

These examples clearly illustrate, that the value of CFM should always be as high as possible while the MPH is a variable parameter. Even though it is essential to effective leaf blowing, it may be compromised based on the intended application of the device if your budget calls for it.

Most importantly, we must always consider the diameter of the pipe!

## Blowing force

As we have mentioned, both metrics are ultimately dependent on the power of the engine. Thus, some manufacturers choose to characterize their devices in this manner. This would be the case for Stihl leaf blowers.

Engines can be characterized in multiple ways. While power is a good indicator of the work generated by the engine, force may be more useful when comparing the ability to move objects. The unit of force is newton – a metric unit that characterizes the acceleration of an object of a certain mass.

Blowing force (opens in a new tab) is an effective way to compare leaf blowers because of the effect of the pipe on CFM. Even though we have mentioned that strictly speaking CFM does not depend on the diameter of the tube, its physical presence does in fact restrict the movement of air. This is due to the friction that the inner surface of the pipe applies to the air. Thus, many manufacturers boost their CFM by measuring it without the tube!

## The ranges

Each different type of leaf blower has CFM and MPH values that fall within a typical range.

Corded Handheld Leaf BlowersCordless Handheld Leaf BlowersGas Handheld Leaf BlowersBackpack Leaf BlowersWalk-Behind Leaf Blowers
Range of CFM ratings145-800 CFM80-900 CFM354-520 CFM375-1245 CFM520-2900 CFM
Range of MPH ratings75-260 MPH75-200 MPH115-250 MPH121-270 MPH143-200 MPH

Those ranges might be surprising, especially for those who weren’t aware of how powerful modern electric leaf blowers are.

However, keep in mind that for all that power, each type of leaf blower has its limitations. A corded electric blower, for example, will be limited by the length of its extension cord, while a cordless blower will have limited battery life.

## The champions

Even though we recommend comparing devices based on multiple metrics, as demonstrated in this article, we would like to present several examples just to show how high their values can get.

We have utilized our database of over 300 leaf blowers to bring you the following champions. Currently, the leaders in their respective categories are:

For the highest CFM, the Billy Goat F1802V, with a CFM of 2900.

For the highest MPH, the Husqvarna 150BT, with an MPH of 270.

## FAQ

### What is the meaning of CFM?

CFM stands for cubic feet per minute, a measure of volumetric flow. It indicates how much air exits a leaf blower's nozzle in one minute.

### What is the meaning of MPH?

MPH stands for miles per hour, a measure of velocity. It indicates how fast air exits a leaf blower.

### What's more important? CFM or MPH?

They are both important and distinct metrics. A higher CFM will help you clear a larger area and push leaves further. A higher MPH will help you better lift wet leaves and debris.

#### Patrick

Manager and editor of leafblowerguide.com. He worked over 10 years for a well-known global company manufacturing outdoor power equipment, before starting his own landscaping business.

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