Manasara 61.6

61.6

dvijarājāyaṃ vāpi mānayed garuḍodayam
pīṭhatārasamādhyardhaṃ pādonaṃ dviguṇaṃ tu vā

One may also measure the height of Garuḍa based on the king of the twice-born (Viṣṇu):
equal to the width of the base pedestal (pīṭha), or one and a half times, or one and three-quarter times, or twice;