selling jewelry? noob

I just sold a necklace

and I used an online scrap calculator to determine the price.. I actually knocked of about 25%.. I don't really know what Im doing but I have more necklaces.. my question... should I not be using the online scrap calculator for actual necklaces.. what is the best way to determine the worth of the necklace and gold I have.. thanks
first off. what is the gold content of your jewelry? if it is 18k it is 750 parts out of 1000 gold or 3/4 gold by weight. 14k is 58.5% gold by weight. so if you have a 14k gold necklace that weighs 10 grams then you have 5.85 grams of pure gold, the rest of the metal is silver and copper with a little bit of zinc. find the gold price of the day, divide that price by 31.1 to get the gram price, add your profit margin to the total and you made money. ie. 10 gram necklace, gold at 1000 per ounce divided by 31.1 = 32.15 per gram you have 5.85 grams of gold in the piece so you multiply by gram price and get 188.07 worth of gold add on your profit margin 2.7 = 507 or there abouts. you can of course make your profit margin hat ever you want. hope this helps
sorry i didn't answer your do not use the scrape calculator as it take a percentage off for the refining process. this is what you would use to buy gold and add a bit to it for market fluctuation, so if you buy x amount of gold and the market is high you pay more for it and then before you can scrap it the market falls you would suffer a loss