The balance sheet contains all of a company's assets and liabilities. Many assets are easy to value because they are tangible goods, easily bought and sold. But patents are not as straightforward because they are intangible. Calculate the value of a patent on the balance sheet using its development costs or purchase price.

Total the development costs for the patent, including research and development costs and associated legal costs. Alternatively, if you purchased the patent, simply use the purchase price.

Spread the development or purchase costs of the patent over its useful life. For instance, if the patent is valid for 17 years -- as most are -- you would divide the costs by 17 to get the annualized value of the patent.

Calculate the current value of the patent by multiplying the patent's annualized value by the number of useful years left in the patent. For example, if the annualized value is $10,000 and the patent has three years remaining, you would value it at $30,000.