The game minecraft is seriously fun! When you have played long enough to be at a stage where you are building nether portals you can use this quick calculator to find where to build your return gate for it to be connected as a pair between the nether and the overworld.
Nether portals make traveling across the overworld much faster, but if you are playing in a world with other players who build gates it's not uncommon to materialize in an unexpected location when stepping through a nether portal.
As it happens, what I needed to do was determine my X,Y,Z coordinates before stepping through the original portal. If I had carried at least ten obsidian and flint and steel with me, on the nether-side of the gate, I could explore to X/8, Y, Z/8 and then build a return portal at that location. I could then activate it with my flint and steel and with any luck it would attach to the gate I came in from. I know I know, this isn't new knowledge it's just that I had not seen the math clearly articulated on pages found by searching at the time.
Note: you can either plug the coordinates in one at a time -or- as a comma separated list (for example 100,66,300). If you only provide two coordinates (such as 100,300) they'll be used to populate X and Z.
Some specific cautions:
Huh, it didn't work?! I believe there are some rare cases in which the gates might not hook up like you expect. If that happens, you may need to do more research to determine what's going wrong. I've had this happen very infrequently, but occasionally it does and I've stepped out of a new gate in a dark ravine or out in the countryside. It seems like it's always above or below the gate I was trying to come back through. (Along the Y axis, though X and Z can be off too. In fact in my case the problem has always been that I was slightly off on my X and Z when building the return gate--and rechecking my coordinates and fixing where the return gate is has solved the problem for me.) However, stepping through a gate into unexpected territory is obviously jarring; So, be prepared. It's always a good idea to carry torches, tools, and supplies.
Thanks for your visit, I hope this helps you. If you find any errors or have suggestions, please let me know. Also, if you are learning web development or wanted to build your own calculator view the source to see how this one works.