There are several brand valuation techniques available, one of which is Market Based Brand Valuation. Other techniques can be found on the links below.
This assumes that there are comparable market transactions (specific brand sales), comparable company transactions (the sale of specific branded companies) or stock market quotations (providing valuation ratios against which a comparable branded entity can be valued). A valuation may be based on the disposal of comparable individual brands, specific branded divisions or whole companies where adequate information is made publicly available.
In practice, there are few directly comparable transactions. Even where there are sales of specific brands or branded businesses, details are generally not widely available, and it is hard to make comparisons.
In addition, the notion of comparability assumes that brands are identical, which is never the case. Market based valuations also tend to be used only as a sense check.