# Thread: Temperature vs Fill Power and Fill Weight

1. ## Temperature vs Fill Power and Fill Weight

I have been trying to get a sense of temperature rating based on fill power and fill weight. I'm sure somewhere there is an equation but in all my searching I couldn't find it. So I took the specifications from Hammock Gears quilts to derive one. I plotted the data and noticed linear trends based on fill power and on the fill weight. From that I derived the following parameters.

mm = -0.005965761
bm = 0.80763296
mb = 0.012018967
bb = 60.8219645

T = temperature
FP = fill power
FW = fill weight

T = (mm * FP + bm) * FW + (mb * FP + bb)

Rechecking the formula, I get values close enough to the Hammock Gear specs to feel like I can use to get a ballpark idea of temperature rating for a down product.
I'm curious if anyone has something better.

2. Ballpark

Think inches of loft. And even then it's highly subjective with far too many variables to predict individual results.

Any method you choose is merely a starting point for discovering what works for you.

3. ## Temperature vs Fill Power and Fill Weight

the biggest factor for warmth is the size of the baffles. you'll see that most manufacturers have nearly the same size baffles for the desired temp range. I think 2.5 inches of loft will be a 20 degree rated quilt from all the quilt makers.

4. Fill power should not matter for warmth as long as the thickness is equal. But at equal warmth and thickness the higher FP will way less in proportion FP difference. As others already said, with down, 2.5" single layer is usually rated at 20F, whether the FP is 700 or 900.

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