So, this is the story and the result of my first try at making and using a schematic for a baby vest. I learned 2 important lessons: make a swatch to figure out the gauge and use a spreadsheet type of file to draw the schematic and calculate. The file I made with an open source software (Open Document Spreadsheet) that anyone can use - is free! I used only basic math formulas that are included in the document. As always, the document can be downloaded from the Patterns section of this site. Let me know if you find it useful!
But lets see an example from my calculations and how you can adapt to your specific project. My gauge is 15 stitches per 10 cm and I needed to figure out how many stitches I need to cast on to cover 59 cm. During primary school I learned to solve this in the following easy way: