Tuesday, August 21, 2012

Why Ratios Matter

At least one good thing came out the Cryo review.  I mentioned in the review that it caused me to rethink how I review stuff.  This post explains that rethinking and adds some more data points to my reviews.  

For a while now I have been using and reviewing folding knives.  There are all sorts of things that I look at, but one of the most important things, one of the things that is almost always present on a good knife and absent on a bad knife is a high blade to handle ratio.  For a while I just listed it because, of course, free blade length is great.  I want a blade that is as small as possible to carry, but as large as possible during use.

To that end, I had originally thought that blade:handle was a good way to measure, objectively, that sentiment.  But over time I have come to realize something.  High blade:handle is not just correlated with a high score, I think it may be the CAUSE OF a high score.  In other words, if you could only know one thing about the design of a knife, I think choosing blade:handle would tell you more about whether it is a good knife than any other feature of design.  Of course you want to know more, but if you had only one thing to look at, I'd say take a peek at the blade:handle.  

Now, I think there is another objective measurement that is valuable to know: blade:weight.  Both ratios are measurements of a knife comparing, essentially how it works when open versus how it carries when closed.  But carrying and reviewing the Cryo and then, with some clear review whipsawing going on, switching to the Al Mar Knives Hawk, I have realized that blade:weight is just as important as blade:handle.

Steel Turd:
 or, Featherweight:

From now on you will see two different ratios: blade:handle and blade:weight in every design section of a folding knife review.  They are objective.  They are clear and easy to understand.  And they are quick and dirty shorthand for a knife that can do a lot of different things but still carry easily.  In the end that is why I carry a folding knife--lots of utility in a convenient package. 

I am also going try this approach in other reviews.  With multitools I am going to highlight the to tools:weight.  Lots of tools for minimal weight is a great thing and a sign of good, conscientious design.  Finally, after carrying the Aeon around for four days and falling in love with it all over again, I think I will add a pair of ratios to the light reviews, one of lumens:weight (with battery) and one of lumens:runtime (max on both). For the curious the lumens:weight on the Aeon is .85 (114 lumens divided by 1.34 ounces) and the lumens:runtime is 1.26 (114 lumens divided by 90 minutes).   

Generally the better knives score around a .70 on blade:handle.   The Sebenza scores a very nice .74.  The Mini Grip does a bit better at .75.  The SOG Flash I scores of the best of any knife I have reviewed, hitting a .78. On blade:weight, I'd like to see a score of 1.  The DF2 ZDP-189 smashes it with a score of 1.875.  The Al Mar Hawk gets a super score of 2.81 (2.75 inches divided by .98 ounces).  Comparatively speaking, the Steel Turd a.k.a. the Cryo gets a score of .65.  Ugh.  That is a lot of weight for nothing.  Multitools are a bit different.  You want a ratio better than 1.  The Skeletool CX has a tool:weight ratio of 1.4 (7 tools divided by 5 ounces).  The Charge TTi hits a really nice 2.32 (19 tools divided by 8.2 ounces).

One other side benefit of the ratios (aside from their shorthand function and objectivity) is that they are unitless measurements meaning they stay the same regardless of whether you are using standard or metric.  Hopefully this will help out non-US readers.

So look for the following in upcoming reviews:


blade:handle (inches:inches)
blade:weight (inches:ounces)


tools:weight (in ounces)


lumens:weight (in ounces; with battery)
lumens:runtime (in minutes)    


  1. I am having a hard time swallowing the value of the blade:weight ratio. Example: Won't this automatically have a negative impact on folders with steel liners versus those without? Now if, by definition, steel liners are not valued then it makes sense. Am I missing something here? How will these ratios be weighed into the 20 point scoring?

    1. For a while now I have been using and reviewing folding knives. There are all sorts of things that I look at, but one of the most important things, one of the things that is almost always present on a good knife and absent on a bad knife is a high blade to handle ratio.
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  2. Purpose is all important. No ratio will determine a score, but I will give them as data points. I generally think steel liners are a waste, Emerson has some good hard use knives without them, but obviously they matter in some applications.

  3. I see, thanks. I definitely think the added info will help me form my own preferred ratio quantifications. As I fiddle with my tools, I learn to appreciate form/function differences between them but I cannot always quantify them.

  4. I like the idea of a blade size to overall weight ratio, and that can probably apply to both folding and fixed-blade knives.

    You could even chart folding knives according to their blade:weight ratios to provide a very clear assessment and objective recommendations. Skeletonized handles might throw things off a bit, but that's nothing an asterisk cannot fix.

    But the blade length to handle length ratio might be tougher to glean usable information from. It doesn't take into account handle width, blade thickness, bulkiness, and other such dimensional nuances. 0.70 might be a sweet spot, but it ignores other factors that might make a knife more or less compact.

    Larger knives will probably also have higher blade:handle ratios and smaller knives lower ratios. Let's say a knife with a 2-inch blade has a 2.75-inch handle, for a ratio of 0.73. A 4-inch knife might have the same 3/4-inch clearance spacing for a handle length of 4.75-inch and ratio of 0.84.

    Such a ratio wouldn't take into account design nuances, such as how the Spyderco Dragonfly has jimping on both sides of the blade. A rough measurement gives a usable blade length to handle ratio of less than 0.6. A gentleman's folder might have a higher ratio, but this wouldn't necessarily mean it's better.

    Dimensions and ratios are objective, but if you have to explain the ratios for different tools they lose their effectiveness in painting a clear picture. Five years from now after you've reviewed a hundred more knives, will you be able to present a chart of blade:handle length ratios without feeling compelled to explain why some great knives score low and poor knives high? If not, then the blade:handle ratio might not be a useful measurement to emphasize.

    All that said, I do appreciate what you're trying to do. Dimensional ratios can be helpful, but they can also be deceiving, especially when values are qualified. Blade:weight ratio is a good idea, imho, because it can be used to create an objective comparative ranking of knives. Blade:handle length, however, cannot or should not be used for comparison purposes, at least not without extensive disclaimers and explanations.

  5. The development of these numbers as one way of looking at what a designer has done seems helpful to me. There are probably knives whose numbers will be totally unrepresentative of what the knife is all about, though. I think it was Mark Twain who said: "There are three kinds of lie: a lie, and damn lie and a statistic!" So it will behoove us all to remember that a ratio is not a rule. For instance, I'd think the skinners I have seen (I'm not the type to ever use one) would be unfairly penalized for the utility of their handle length vs. their blade length. Of course, I'm just speaking as an English major, and even though we're usually right, I could be wrong. How do these numbers differ from the average of a group of reasonably good to excellent fixed blades suitable for EDC? I like the fact that you keep thinking about things. Don't stop.

    Bill B.

  6. Good idea on the ratios and good comments here. These ratios will provide a good snapshot but there is always more to the story. Namely, intended use, level of duty, cosmetic appeal, and feel in hand. I might add that weight balance is almost as important of weight itself. Good stuff. Thought provoking.