Tutorials/Measuring distance

"You can't manage what you don't measure." -Matt Keiser

Official Units of Measure
Distances in Minecraft are quite easy to measure. Officially, Minecraft uses the metric system, and each block is considered to be 1 cubic meter. To measure long distances, then, simply place a torch or other marker object every ten blocks. Place a second marker at each tenth marker to mark 100 m distances, and at ten of these, you have one kilometer. Try placing a sign at each km, just like road signs in the real world.

Conserving Markers
If the measurement is being taken above ground, and lighting the entire path is not necessary, place the markers as above. When 100 m is reached, the 10 m markers can be removed and reused for the next 100 m run. This allows for the path to be constructed without having to count 100 blocks at a time, while still allowing the markers on the completed path to be easily followed without using too much material.

GPS
If you press F3, the Debug screen will give you your present location in X-Y-Z co-ordinates. Measuring distances between two locations or waypoints is as easy as subtraction, if you walk in a cardinal direction. Otherwise you will need to make use of the Pythagorean theorem to solve the distance. Not strictly in-game, though.

Using the Imperial System
Some may wish to measure distances in miles instead of kilometers. There are two methods of doing this.

Converting km to mi
One mile converts to approximately 1609 m. To simplify, consider a mile to be 1600 blocks long. Instead of placing your initial markers every 10 blocks, place them every 16 blocks, which is one hundredth of a mile. As before, double markers go every 10 markers, and then one mile is 10 double markers.

Using Yards
Instead of considering one block to be 1 meter long, pretend that a block is 1 yard long instead—after all, the game world is entirely subjective! One mile is exactly 1760 yards. Place your initial markers every 16 blocks, and your double markers at every 11 markers rather than every 10. Thus, a double marker measures 16 × 11 = 176 yards, or 1⁄10 of a mile.