What does “measured with Plus12” mean?

Recently, we have been asked a lot what it means that the shoe length has been measured with a Plus12. Let's explain a little. Plus12 is a measuring tool that can measure both the length of the foot and the inside length of the shoe. When measuring the foot, the heel is placed on the inside of the measuring tool and the longest toe is set under and behind the tip of the measuring tool (see pictures). This gives a measurement that shows the length of the foot and adds 12 mm to it. Why 12 mm? This is the recommended margin when buying shoes. In order to get the length of the foot, 12 mm must be subtracted from the reading. For example, if Plus12 shows 22,2 cm when measuring the foot, the foot length is 21 cm. The inside length of the shoe you are buying should be 22,2 cm (depending on how much margin you want).
When measuring the inside length of a shoe, the measuring tool is placed inside the shoe. In this case, the back end of the measuring tool is placed in the heel of the shoe (where the heel actually extends into the shoe) and the front end of the toe is pushed into the furthest front end of the shoe (usually above the big toe). This gives the length that the foot can actually use in the shoe.
If you measure the length from the insole, you may not get the same reading, because there is usually more space in the shoe than the length of the insole.
So, if the online store says that the length was measured with a Plus12, you don't have to subtract anything from this reading, but this is the actual space inside the shoe that the foot can use. These measurements may be different because each measurer presses the tool with different force and may push the tip of the measuring tape to a different place in the shoe.
So remember that when measuring the foot, you need to subtract 12 mm from the Plus12 reading, but not when measuring the shoe length.
You can purchase a Plus12 measuring device for yourself from here.
It is from herewhy the Plus12 metric is used at all.

Images from plus12socks.com ja bosenogice.si from the leaves.