A 40-Pound Sword?
By C. Jarko
One of the most outrageous (and wildly incorrect) statements made about Medieval swords is that they were heavy and weighed as much as 40 pounds. While the fact that this statement even came once from a respected scholar and expert on Medieval warfare is surprising, it's not at all an uncommon claim. Let's take a look at just how large a sword would have to be to weigh that much or anywhere close to it.
Simple Science (with a little algebra thrown in): How do we know Medieval swords weren't 40 pounds (or for that matter, even 15 or 20 pounds)? The answer is density. Density is a way of expressing how much an object (of a certain size and of a given material) weighs. The size of the object is expressed in terms of its volume. Volume is the size of an object as measured by its length, width and thickness (or height) and is expressed in cubic inches. Written as a mathematical equation, it looks like this:
V = L x W x H.
One cubic inch is one inch long by one inch wide by one inch thick.
For the purpose of this discussion, we can use a simple three-dimensional rectangle to represent our sword. Let's pick a typical longsword with an overall length of 48 inches and a general width of 2 inches (the widest part of the blade). We'll get to the height later.
Swords were made of carbon steel, which has a known density of roughly 0.284 pounds per cubic inch (lbs/per cubic inch). If we know how much weight we have (in this case "40" pounds), we can figure out how many cubic inches the object would have:
40 pounds divided by 0.284 (the density of steel) = 140.85 cubic inches (the volume or "V" of a 40 pound sword).
Our sword is 48 inches long, 2 inches wide and "H" inches thick, thus: V = 48 x 2 x H. Using our volume of 140.85, we can solve for H for which we get:
140.85 = 48 x 2 x H
140.85 = 96 x H
H= 1.47 inches (140.85 divided by 96)
This means our steel sword is 48 inches long, 2 inches wide and 1.47 inches thick along its entire length. This would definitely be a blunt object and not a sharp cutting instrument like a sword.
Just for fun, let's see what we get when we say a sword (again 48 inches long and 2 inches wide) weighs 15 pounds or 10 pounds:
15 pounds divided by 0.284 (the density of steel) = 52.82 cubic inches (the volume "V" of a 15 pound sword).
Using our volume of 52.82, we can solve for H:
52.82 = 48 x 2 x H
52.82 = 96 x H
H = 0.55 inches (52.82 divided by 96)
That's over half an inch thick, still a blunt object. Let's try one more time for 10 pounds.
10 pounds divided by 0.284 (the density of steel) = 35.21 cubic inches (the volume "V" of a 15 pound sword).
Again, we can solve for H:
35.21 = 48 x 2 x H
35.21 = 96 x H
H = 0.37 inches
That's almost three eighths of an inch thick. If you look at three eighths of an inch on a ruler, you'll see we are now starting to get "sword-like" but we're still not there.
If we do the math using the thickness of a real sword (say an average 1/8th inch thick across a roughly 48" by 2" rectangle) it turns out such it weighs a reasonable 3.408 pounds. Which, when you take into account things like differential cross-section, distal taper, edge bevel and overall taper of the blade geometry, as well as the weight of the pommel and cross, then an average weight of 2.5 - 3.5 pounds works out just about right. So, the next time
When someone says "a longsword weighs 15 pounds", you can reply, "Oh, like this?" as you hand them 15 pounds of a half-inch thick steel slab four feet long and two inches wide. There's nothing like holding the truth in your hands. If there were really battle swords that actually weighed 40 pounds, or even just 15 or 20 pounds, then where are they? Why don't we have a single historical example as proof? It would be such an easy thing to prove. So, if you have a modern made sword which you bought and it weighs far more than the real life working versions of history, no matter what the manufacture claims, that sword is just not made correctly.
When we use the mathematical proof, we need to understand that there are variables which we aren't taking into account here, but this line of argument works well enough to debunk the more outrageous claims about sword weight. The next time you're arguing with someone who refuses to budge off their claim that swords were very heavy and unwieldy, you can tell them: "Hey, you do the math!"
