Down weight calculation

[sdf]

I'm in the process of making a quilt, and I'm trying to figure out how much down to use. If 9 oz of 900 fill down provides a certain temperature rating, how much 800 fill down will it take to get the same rating? I know temperature ratings are not so precise, but is is there a way to "convert" one fill power to another?

[squidbilly]

I'm doing the same thing this weekend! The fp tells you how much space the down fills up, not the comfort level.

If the chambers of your quilt are 900 cubic inches in volume (length x width x height), then you need one ounce of 900 fp to fill each one.

You will need 1.125 ounces of 800fp to fill the same space. (900ci divided by 800fp)

If you're a cold sleeper- add a little overfill.

[sr1355]

You need to allow for over stuff, most vendors are using 120%-130% so if a chamber volume is 900 and your using 900 you'll need 1.2-1.3oz to achieve desired over stuff. This will provide some stability of down in the chamber. At 100% you have too much down shifting and result will be cold spots....

[squidbilly]

Thanks Paul.

[Gravity]

This spreadsheet helped me with my down calculations:
https://docs.google.com/spreadsheet/...hl=en_US#gid=6

[sdf]

This spreadsheet helped me with my down calculations:
https://docs.google.com/spreadsheet/...hl=en_US#gid=6

Cool spreadsheet, but why does the Minimum Finished Weight box say 1923.7 oz?
Even if that were grams it would be almost 68 ounces.

[Cranky Bear]

I have always found this to be helpful-

http://thru-hiker.com/projects/down_quilt.php