Herodotus gives a detailed description of the Persian fleet that assembled at Doriskos in spring 480 BC (see table).
However, after the fleet was struck the storm off the coast of Magnesia, approximately one third of the fleet was lost.
Thus, by Herodotus's reckoning, the Persian fleet would have had approximately 800 triremes at Artemisium.

Some modern scholars have accepted these numbers, especially since the ancient sources are unusually consistent on this point.
Other authors reject this number, with 1,207 being seen as more of a reference to the combined Greek fleet in the Iliad, and generally claim that the Persians could have launched no more than around 600 warships into the Aegean.
Herodotus gives a detailed description of the Persian fleet that assembled at Doriskos in spring 480 BC (see table). However, after the fleet was struck the storm off the coast of Magnesia, approximately one third of the fleet was lost. Thus, by Herodotus's reckoning, the Persian fleet would have had approximately 800 triremes at Artemisium.
Some modern scholars have accepted these numbers, especially since the ancient sources are unusually consistent on this point. Other authors reject this number, with 1,207 being seen as more of a reference to the combined Greek fleet in the Iliad, and generally claim that the Persians could have launched no more than around 600 warships into the Aegean.
Battle of Artemisium