A normal room — one light layer head to toe.
For a baby of 6–12 months, awake, in a 20°C (68°F) room: long-sleeve bodysuit, pants and socks.
Short sleeves from 21°C, covered arms below.
Pants below 21°C, lined ones below 15°C.
Socks below 24°C, warm ones below 15°C.
0–3 months: long-sleeve bodysuit, pants and socks. 3–6 months: long-sleeve bodysuit, pants and socks. 6–12 months: long-sleeve bodysuit, pants and socks. 1–3 years: T-shirt and socks.
At 19°C the answer stays the same.
At 21°C it changes to short-sleeve bodysuit and socks.
Runs warm: the app dresses a touch lighter, short-sleeve bodysuit and socks.
For sleep in the same room, the app suggests long-sleeve bodysuit, in a 2.5 TOG sack.
No hat indoors — a baby cools through the head.
Check the neck — warm but not sweaty means just right.