Here are five common factors that often determine the worth of an invention. (1) Importance of a Patent: For breakthrough patents, a.k.a. foundational patents, the patents are so innovative that they give the owner a complete monopoly over an entire industry and are extremely valuable, often worth billions of dollars. Although most patents never reach these heady heights they are nevertheless valuable in that they can force a competitor to start innovating to keep pace with new and improved technologies and products in the market. Incremental patents, which make only small advances over existing products, are usually the least valuable though this may not be always so. A question that is often asked in relation to endeavoring to put a price on a patent is 'How much would my competitors pay to use my protected product or process?' (2) The Market: Market size, the number of products that are likely to be made and the cost of each product also have a significant bearing on the value of a patent. What sort of sales can the patent be expected to support, and for how long? A good example of an article which has significant market presence is the ubiquitous Intel chip that is reported to have a value estimated in the billions of dollars. (3) The Patent Term: Patents have a maximum life of 20 years and, therefore, a 20-year potential monopoly. Patents that are just beginning their life and which have longer to run on the their potential monopoly position understandably will have more value. It is rare that a patent nearing the end of its term will cause a great threat to its competitors. It is almost certain that they will have devised technologies or products of their own by then that will not interfere with the patent owners monopoly position. In addition, one has to take into consideration the potential business life of a patent, i.e., the duration, which a patent is likely to be economically useful, if other subsequent patents are providing better alternatives to it. (4) Amount of Prior Art: The number of cited documents or patented products populating an area of innovation also has an effect on the value of a patent. Generally, if the particular product is one of many products of a similar type then the consumers' options de-value the patent of interest, yielding a relatively smaller premium than, for example, a stand alone patent with a captured customer base and no adjacent competition. (5) Patent Significance: Every patent has its own significance in a particular area and will usually form part of an overall IP strategy either to maximize its earning potential or to allow other patents to maximize theirs. Examples of such patents are those that are used to block other key players from gaining a foothold in a market. Yet other examples are those patents that are additional to an original patent and rely on the protected matter in the original patent to successfully operate. It is not uncommon for drug companies or telecom companies to take out further patents protecting a strong first generation of patents, thus securing a big chunk of a market and the ability to negotiate licenses and royalties from the protected, but much desired technology.

In the U.S., the inventor has a "first to invent" claim which is different from other patenting organizations throughout the world who generally utilize "first to file." Debate over this issue, and which model best influences economic development is ongoing. Some are concerned that a change in patent rights may harm the small startup and benefit the incumbents with deeper pockets. You can read more about this topic.

A plant patent covers asexually reproducible plants (that is, through the use of grafts and cuttings), such as flowers. Sexually reproducible plants (that is, those that use pollination), can be monopolized under the Plant Protection Act. Both sexually and asexually reproducible plants can now also be monopolized by utility patent. Plant patents are comparatively recent innovations, the first one being granted in 1930. A plant patent is granted by the Government to an inventor (or the inventor's heirs or assigns) who has invented or discovered and asexually reproduced a distinct and new variety of plant, other than a tuber propagated plant or a plant found in an uncultivated state. The grant, which lasts for 20 years from the date of filing the application, protects the inventor's right to exclude others from asexually reproducing, selling, or using the plant so reproduced. This protection is limited to a plant in its ordinary meaning: (1) A living plant organism which expresses a set of characteristics determined by its single, genetic makeup or genotype, which can be duplicated through asexual reproduction, but which can not otherwise be "made" or "manufactured." (2) Sports, mutants, hybrids, and transformed plants are comprehended; sports or mutants may be spontaneous or induced. Hybrids may be natural, from a planned breeding program, or somatic in source. While natural plant mutants might have naturally occurred, they must have been discovered in a cultivated area. (3) Algae and macro fungi are regarded as plants, but bacteria are not. A utility patent would be filed for claims to plants, seeds, genes, etc. According to the USPTO, there were 959 plant patent applications filed in 2009.

There are three types of different patents (1) Utility Patents: Issued for the invention of a new and useful process, machine, manufacture, or composition of matter, or a new and useful improvement thereof, it generally permits its owner to exclude others from making, using, or selling the invention for a period of up to twenty years from the date of patent application filing ++, subject to the payment of maintenance fees. Approximately 90% of the patent documents issued by the USPTO in recent years have been utility patents, also referred to as "patents for invention." (2) Design Patents: Issued for a new, original, and ornamental design for an article of manufacture, it permits its owner to exclude others from making, using, or selling the design for a period of fourteen years from the date of patent grant. Design patents are not subject to the payment of maintenance fees. (3). Plant Patents: Issued for a new and distinct, invented or discovered asexually reproduced plant including cultivated sports, mutants, hybrids, and newly found seedlings, other than a tuber propagated plant or a plant found in an uncultivated state, it permits its owner to exclude others from making, using, or selling the plant for a period of up to twenty years from the date of patent application filing. Plant patents are not subject to the payment of maintenance fees.

In Article I, Section 8 of the Constitution of the United States it says, " Congress shall have power [...] to promote the progress of science and useful arts by securing for limited times to inventors the exclusive right to their respective discoveries."