how to calculate wattage needed for system

Gupta_

Prominent
Feb 18, 2017
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my build:
i5 6600 w/ stock cooler
asus b150 pro gaming aura
g.skill 2x8 16gb ddr4 2400 set to 2133
msi gaming x rx 480 4gb
crucial mx 300 575gb m.2 sata
wd blue 1tb 7200 rpm/6gb/s sata/64mb cache
phanteks eclipse p400 case
5 120mm case fans

how do i calculate the total wattage used for these parts? is it listed somewhere in the parts descriptions or do you just need to estimate? I will be using a 80+ gold seasonic psu, but want to buy the lowest wattage that will work perfectly. no upgrades ever