When I Ebay something, How do I determine what to put down as shipping costs?

— Package it for shipping, weigh it and the post office web site can give you a cost.
—In the US, Priority Mail flat rate boxes can be a very good bargain, the price is the same even when shipping to Hawaii or Alaska.
—The USPS will send you the boxes for free, you can order online
—Free shipping can be a good selling point, you might get more bids and actually make more money. But still package and weight before you try to figure out if that might work.

You can also go on Paypal to figure out and print postage. But you do need to know the weight. Or get those flat rate boxes from the post office-although they seem quite high to me.

Just an idea: don’t change a handling fee or much more than the shipping costs (factor in $1 for the box, though). Outrageous S&H fees really turn off Ebay buyers.

I disagree with @crankywithakeyboard about not charging for handling fee. You should factor the cost of your time and effort to ship an item. If you have to go out of your way to take the item to a post office or to a (UPS or FedEx) shipping center then you should consider the cost of gas to drive out there and back as well as the time you spend doing so. Most likely, your item will sell for cheap, and after the sale Ebay will be charging you a Final Value Fee. When you get the payment via PayPal, you don’t get the whole amount either, since PayPal will be charging you the usual transaction fee which comes out to about 3%. If you don’t wise up, you’ll end up practically giving away your item while going through all the trouble of a quick shipment to try and please the buyer hoping that they’ll give you a positive feedback.

I am an Ebay Power Seller and a Top Rated Seller.. and have been selling on ebay for over 10 yrs. Take my advise.. people HATE Handling Fee’s and figure out how much it will be to ship at www.usps.com by using the weight and size of the package.. THEN add it in your cost and offer FREE USA shipping. Free shipping is a great bonus.. and will get your item looked at before any others.