Goodwill makes up a significant portion of the value of a business but, due to its intangible nature, it can be difficult to assess its value.
The value of your goodwill be higher if you have a good standing in the community, you have solid relationships with your customers and suppliers, or you have protected intellectual property that gives you an advantage in the market.
There are several methods used to calculate goodwill, however, most importantly, the value will be what someone is willing to pay for your business. Find a professional to help with the valuation if you are unsure.