When you are shopping for a new knife, either your first or your fiftieth, you probably look at the specs at some point. Handle length, blade length, weight, and so on. But after years of reviewing knives, the two most important specs in understanding how good a folder is and how it will carry are rarely listed. Time has shown me that two ratios, blade length to weight and blade length to handle length ultimately are more informative than any other specs on a knife.
Generally, I don’t carry folders that weigh more than four ounces, as any heavier and it is probably better to carry a small fixed blade. Additionally, because of complicated, state-by-state laws, I usually carry a knife with a blade under 3 inches (consult your local knife laws for more information).
These two basic numbers – a knife’s blade size and total weight – however, don’t really tell me how capable a knife is given its footprint in my pocket. For that, we need to look at the blade:weight (b:w) and blade:handle length (b:h) ratios. Here is a closer look as to why.
Blade:Weight (1:1 or Better)
If you have decided to carry a folding knife, you are prioritizing convenience, and no single number better expresses convenience in a folder than its blade to weight ratio. In essence, this is a measure of how much cutting power you get for the knife’s “felt” size. While the length of a knife can be hidden in a pocket, there is no way to make a knife “feel” lighter, and so, in the end, blade to weight gives you the best sense of what a folder can do versus how it will carry.
In all of the performance ratios, the Al Mar Ultralight series is at the top of the scale. Thanks to linerless micarta handles and some serious attention to measurements, nothing in the knife world comes close to the Al Mar Ultralight Hawk, with a blade:weight of 2.81 and a blade:handle of 0.84. The Ultralight is not the sturdiest knife in the world, but if you don’t need to thump on your blade and are concerned about carry, it is a good place to start. A warning though—for all of the spec beauty, the Hawk is quite expensive for what it is—a folder with AUS8 steel and no pocket clip.
Other knives with superlative b:w include: the Spyderco Dragonfly (2.0), the AG Russell Light’n Bug (2.5; AG Russell is also a company that pays attention to the performance ratios), the Cold Steel Mini Recon (0.83), and Spyderco Manix 2 LW (1.15).
Blade:Handle (Approaching 0.75)
This is really just a matter of space—there is no way (aside from clunky designs like the Benchmade LFK) to get a blade as long as the handle. There are a few cheats; recurves, for instance, pack a longer cutting edge than non-recurves with the same blade length. Designers can also push pivot screws as far forward on the handle. In the end though, we will never see a 1:1 ratio without some contraption or cheat like the one seen on the LFK. The key here is that b:h tells you how much cutting capacity you have in knife of a given size.
If your knife blade is big enough to span an apple, but still rests in a reasonably sized handle, it feels like your getting something for nothing. Note that some designs, like the Spyderco Delica and the Paramilitary 2, are purposely designed with a longer handle (for better grip), but aside from these designs, you want a b:h as close to 1:1 as you can get. In reality, anything better than 0.75 is quite good (and quite rare).
Again, the Al Mar Ultralight Hawk is the best knife I have found in this regard with a b:h of 0.84, but there are other very impressive folders in this regard. The aforementioned Manix 2 LW ties the Hawk with a b:h of 0.84. The AG Russell K12 One-Handed Knife has a b:h of 0.80 (and a b:w of 1.03). The SOG Flash I has a b:h of 0.78.
If you are looking for a new knife, it pays to go beyond the list of normal specs. Blade to weight and blade to handle ratios tell you a lot more about a how a knife will carry and what it will do than a list of inches and ounces. If car aficionados know that power to weight ratios are key to understanding car performance, these ratios are the same things for knives.