KR barracks have the same basic HPs across the platforms:
Militia 50
Footmen 100
Knights 150
Holy Order 200
Barbarian Mead Hall 250
HPs are increased with all barracks star upgrades, more so on flash than the others:
[On mobile and Steam]
Militia (+10) 60
Footmen(+20) 120
Knights (+30) 180
Holy Order (+40) 240
Barbarian Mead Hall (+50) 300
[On flash]
Militia (+22) 72
Footmen(+44) 144
Knights (+66) 216
Holy Order (+88) 288
Barbarian Mead Hall (+110) 360
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More specifically,
Toughness Training upgrade increases HP by
5/10/15/20/25 on mobile and Steam. 16/32/48/60/80 on flash.
Endurance Training upgrade increases HP by
5/10/15/20/25 on mobile and Steam. 6/12/18/28/30 on flash.