The pattern now includes an estimate for how many skeins are required. However, there are lots of caveats so please read on...
First, please be aware these are only best guess estimates. I believe I have made them liberal estimates, so you may have a skein or two left over. But I thought that far preferable to finding out that you have run short and then can't find the same dye lot at your local yarn store. Please let me know if you ever have it turn out that the estimate was too short. I do not want that ever to happen to anyone. But also if you have more that one or two extra skeins at the end, let me know that too. (The best place to communicate with me is in the PhranckoForum.com, rather than in comments here. Thanks!)
If you do not provide the yards or meters in each skein of your chosen yarn when entering the yarn data from the band, then of course the number of skeins can't be estimated. So then the estimate shows in yards and meters.
Sometimes you may not see a yardage estimate in the yarn description in your pattern. Instead you will see "[sorry, no yardage estimate]." There are a couple reasons this may occur. If your stitch gauge is less than 3 (i.e., 12 sts in 4") or greater than 7.5 (i.e., 30 sts in 4") sts per inch or if the ratio of row gauge divided by stitch gauge is not between 1.2 and 1.55, then I think any attempt to estimate would simply be too far off. This should cover all common cases using Sport (#2) to Bulky (#5) weight yarns in Stockinette stitch. Of course you may use any stitch you like, but if the gauge falls outside of these ranges, you will have to estimate the yardage yourself.
This is an experimental attempt to estimate the yardage. I have tested it against all of my published patterns and it seems to work quite well. But I certainly cannot test it against every possible gauge that you may use. So let's work together to perfect this over time by letting me know if it works, or if (horrors!) you did not have enough skeins, or if there were way too many left over.