How are royalties calculated for licensing a WARF technology?

Royalties, paid when products using the technology are sold, may be calculated on a percentage-of-sales or fee-per-unit basis. WARF expects a minimum royalty each year after an agreed upon development period. This fee is designed to encourage timely  commercialization and active marketing of the technology and is set at a relatively low amount compared to the expected royalties. Any royalties actually earned offset that minimum; it’s usually not an additional fee.