CLO.

CLO — what to wear today in Paris

13°morning
low

3 m/s wind · 13 % rain

Paris

Wed 10 Jun

Roland · forecast 16:27

HOODIE. JEANS. GO.

0.90 CLO. THE PHYSICS HAS SPOKEN, CHAMPION.

THE GREY HOODIE HAS BEEN ACTIVATED. TRUST THE LAYERS.

  • ▸DRY MORNING, WET 16H. RAIN AT 65% — THE WATERPROOF RIDES ALONG ALL DAY.
  • ▸UV 6 TODAY. SUNGLASSES. YOU'LL LOOK INCREDIBLE.

Your day · tap a segment

RUNS 0.3 CLO WARM — CARRY THE TOP LAYER, WEAR THE CONFIDENCE.

The day · drag to scrub

 

07hcommute bands shaded21h

The core — desk-proof, worn all day · 1.18 clo

  1. Black t-shirt

    base

    0.08

  2. Grey hoodie

    mid layer

    0.34

  3. Grey lambswool sweater

    mid layer

    0.36

  4. Black jeans

    legs

    0.24

  5. Brown leather boots

    feet

    0.10

+ the shell — for outside · 0.36 clo

  1. Navy rain shell ☔

    outer

    0.36
1.54clo, full kit
1.18 at the desk
deskwalk
0.36 shorts + tee0.61 trousers + shirt1 winter indoor2 winter coat
Show me the math

Your body walking produces 2.5 MET × 58.2 W/m²; about 78 % of it leaves through your clothes (the rest: breath + sweat) → 113 W/m².

Insulation needed to lose exactly that at 13 °C:
I_total = (33 − 13) / (0.155 × 113) = 1.15 clo

The air film around you insulates too, but 3 m/s of wind erodes it: I_air = 0.7 / (1 + 0.5 × 3) = 0.26 clo

Target = 1.15 − 0.26 = 0.90 clo

The desk is the unit's own definition: 21 °C, seated, still air → 1.04 clo. That's what the core is sized for.

Assumptions and what they get wrong: how it works.