It depends on three things and nothing else: the finished area, the yarn weight and the stitch. A worsted weight throw around 50 by 60 inches in single crochet runs well over a thousand yards, and the same blanket in double crochet uses noticeably less, because taller stitches cover more area per yard. Put your own numbers in above rather than trusting a rounded figure from a blog.
A single crochet is short and dense, so it takes many more stitches to cover the same square inch. Double and treble crochet are taller and more open. Same yarn, same blanket, and the yardage can differ by a third or more purely on stitch choice.
Buy more than the estimate, and buy it in the same dye lot. An estimate assumes an even tension and no frogging, and neither survives a real project. Yarn left over is a hat. Yarn that runs out three rows from the end in a discontinued color is a different project entirely.
The estimate is in yards. Metres are yards multiplied by 0.9144, so a thousand yards is about 914 metres. Yarn bands usually print both.
Wovely keeps the pattern, your place in it and what you have in your stash together, so the project you started in March is still findable in September. This calculator stays free whether you sign up or not.