Why does warm light feel cosier? Slide the kelvin and see

The number on a bulb box, like 2700 K, is its colour temperature, and lower means warmer. Slide it from candle-flame orange to daylight blue and watch the same living room change, then see which kelvin suits which room.

Cosy rarely means buying more: swapping one bulb is often enough. Check the cap, the shade and the kelvin number before you buy.