To make a sword out of the blood, you will have to kill 359 people to get enough iron from their blood. This may seem weird, but it’s actually true that to make an average long sword, you need the blood of at least 359 people. It can be proved in the following way. Yss

The weight of an average British long sword lies between 1.1 and 1.8 kg. Let’s consider the middle value i.e. 1.45 kg.

The iron content of the long sword lies between 0.002% and 2.1%. Let’s take the median carbon content 1.051%.

So, the total amount of iron in the long sword will be 1.45 kg – (1.45 kg * 1.051%) = 1.4347605 kg.

The blood of an average person contains 4 grams i.e. 0.004 kg of iron.

Thus, to make an average long sword, we will need iron extracted from the blood of (1.4347605 / 0.004) = 358.69 i.e. 359 people. Proved!