I'm not going to lie to you, the easiest and cheapest way to calculate shipping is by selling your products through a website or shop.
However, I understand that when you're first starting out, it isn't always possible to do it that way.
Let's not forget, I've been where you are, and I'm here to help.
Here are 2 ways I used to ship my products before ever having an online shop.
Head over to the USPS website at www.usps.com, and click "Calculate a Price".
Now, for this, you will need to have your customers zip code, and a general idea of what your package size and weight will be. The more often you ship, the more you'll start to be able to tell how much something will weigh just from the looks of it.
Form there, you'll be shown a list of different shipping services, each priced at different amounts.
What I would do from there is take the estimate of the First Class Package Service, and the Priority Mail Service, and offer both options to my customers. If you're worried that your weight may not be right, I would increase the price estimate by $1 or $2, just in case, and then give that price estimate to your customer. From there, they can decide which shipping service they would prefer, and you simply add it on to their invoice.
Easy peasy right?!
Head over to www.paypal.com/shipnow and type in your return address, and your customers shipping address.
You'll get to choose between a few shipping services based on the estimated package weight and shape, and then be given the shipping estimate.
You can then purchase the shipping label, and print it out directly from that page!
Want to save on all those shipping labels? Sign up for a FREE Paypal Business account.
Read all about my thoughts on a Paypal Business account here.
Let me know which shipping program you prefer!