Using the Spanish future perfect to talk about the past (El Futuro Perfecto)

El Futuro Perfecto for suppositions about the past

In Spanish, we use El Futuro Perfecto to make a supposition about something that happened in the past.

For example:

In English this supposition is generally expressed with "must have".

In Spanish we don't need to add anything to the sentence to express that supposition/probability. The use of El Futuro Perfecto includes that nuance.

The use of El Futuro Perfecto with this nuance will very often be triggered by a question or previous comment using El Pretérito Perfecto or El Presente for example:

See also Conjugate regular verbs in the perfect future in Spanish (El Futuro Perfecto) and Conjugate Spanish irregular verbs in the perfect future in Spanish (El Futuro Perfecto) 

For a different way to make suppositions about the past see also How to say "must have [done something] in Spanish with the verb deber