The future perfect tense in Spanish consists of the future tense of the verb haber and the past participle.
(yo) habré + past participle
(tú) habrás + past participle
(él/ella/Ud.) habrá + past participle
(nosotros) habremos + past participle
(ellos/ellas/Uds) habrán + past participle
Just like in English, the future perfect tense describes an event that will be completed in the future before another separate event occurs.
- Lo habré terminado todo antes de irme a Lima, Perú. I’ll have finished everything before I go to Lima, Peru.
- Habrán descansado antes de ir al cine. They will have rested before going to the movies.
Deber de + infinitive can be used to express probability in the past time.
- Yesica debe de haber ido de compras. Yesica must have (probably) gone shopping.