Actually, if you are buying silverware or old silver jewelry on Ebay there is a fair bit of math needed to convert the weight to actual troy ounces of silver.
Sterling is 92.5% silver and there are 12 troy ounces to a pound, not 16. Spot silver prices are always quoted as Troy ounces of pure silver.
So a calculator that let you enter weight as ounces or grams and the current spot price to calculate the value would be useful.
Whether you can get ranking and traffic and uses is another question...