Layering System Calculator

Clothing layers from activity level and temperature.

Temperature (°F)

Wind speed (mph)

Activity Level

Precipitation

Tab to move between fields

Required CLO value

1.46

Wind chill (°F)34

Effective temp (°F)42

Base layer1

Mid layers1

Wind shell0

Insulated jacket0

Total layers2

How to Use This Calculator

Enter the ambient temperature (°F) and sustained wind speed (mph) you expect.
Select your activity level (sedentary/camp, light hiking, moderate hiking, or strenuous climbing) and expected precipitation (none, light, or heavy).
Read the required CLO value along with the wind chill and body-heat-adjusted effective temperature.
Check the base layer (0 = none/light, 1 = synthetic, 2 = heavy merino) and the number of recommended mid layers.
Review whether a wind shell or insulated jacket is recommended, and the total layer count for the conditions.

How the result changes with Temperature (°F)

Required CLO value: Clothing insulation needed. 1 CLO ≈ a light fleece layer.
Wind chill (°F): Effective temperature accounting for wind (NWS formula).
Effective temp (°F): Wind chill adjusted for body heat from activity.
Base layer: 0 = None/light, 1 = Synthetic wicking, 2 = Heavy merino wool.
Mid layers: Number of insulating mid layers (fleece or puffy).
Wind shell: 1 = Wind shell recommended, 0 = Not needed.
Insulated jacket: 1 = Down/synthetic puffy jacket needed, 0 = Not needed.
Total layers: Total number of clothing layers recommended.

Identify Input Parameters
4 parameters
Temperature (°F) = 40, Wind speed (mph) = 10, Activity Level = 2, Precipitation = 0 = 4 input(s) provided
Calculate Required CLO value
Required CLO value
1.46 = 1.46
Calculate Wind chill
Wind chill
34 = 34
Calculate Effective temp
Effective temp = windChillF + activityHeat
42 = 42