Weight Conversion (oz to grams and vice versa - look at the label on your skein for information)
Do I have enough yarn ... Conversion from Skein (what's in your stash) to Weight (called for in the pattern)
No. of Skeins
How much do I need to buy ... Conversion from Weight (what the pattern calls for) to Skein (what my store sells)
Disclaimer: Remember this is a weight conversion calculator, not a substitution calculation. Sock, sport, worsted-weight, etc all should be converted to the same type yarn before making any calculations.