For example a jacket with 6 ounces of 800 fill down will be substantially warmer than a jacket with 3 ounces of 800 fill down that s double the amount of insulation.
600 fill down jacket temperature range.
The naked body has a clo value of zero and a clo value of 1 is.
A 600 fill power down jacket with an 80 20 down to feather ratio will be warmer than a 600 fill power jacket with a 70 30 ratio.
The image below illustrates the difference in volume between a gram of 600 a gram of 700 and a gram of 800 fill power down.
Like most of the parkas in our collection it features 700 fill power and 13 ounces of white goose down.
It is a much better insulator than feathers and thus is preferred in good jackets.
Down jackets are good for mild exertion level activity.
The down fill weight is one way to tell though it s not strictly a measure of a jacket s warmth it s only a measure of the total weight in ounces or grams of the down in the jacket.
So in simple terms the higher the fill power of a down jacket or sleeping bag the warmer it will be for its weight.
How much insulation is in the garment is obviously an important factor in warmth but not the only one because down comes in a range of quality ratings.
The fill power rating can range from 300 to 900 and above.
But if you are comparing 6 ounces of 600 fill down against 3 ounces of 900 fill down the calculation becomes trickier.
The more insulating air pockets down traps the warmer it will keep you.
A high quality rating starts at about 550.
Fill power ratings range from 300 to 900.
In terms of jacket weather ratings the higher the number the warmer the down.