# Thread: Determining Warmth of Karo Step Top Quilts

1. ## Determining Warmth of Karo Step Top Quilts

How do you determine warmth of Karo step quilts

2. Warmth is derived from the average thickness of unconstricted down. In other words, don't worry about the hills & valleys in your finished quilt. Simply multiply the ounces of down by the fill power rating. Then multiply the length by the width of the quilt. Finally, divide the product of the ounces times FP by the product of the length times width. That will give you the average loft of that amount of unrestricted down.
(oz of down x FP)/(length x width).

I use Western Mountaineering's formula for determining what temperature that loft will give me.
Temp = -18*Loft + 67 [Temp in F' & Loft in inches]

Your actual thickness of the quilt will vary, no matter what baffling technique you use. But that isn't what determines the warmth. It's the amount & quality of the down spread over a quilt of a certain area.

3. ## Definition of loft

Mike:
That's a per layer estimating equation or rule of thumb, applicable with loft defined the way hmmckers look at their quilts: per layer. In the sleeping bag world, including WM's charts, loft is sometimes reported for two layers, top and bottom.

4. So how much would it differ from that, im sure the sleeping bag companies account for the insulation under you being compressed

5. That's per layer. In other words, only the down on top of you is considered in that calculation. But your point is taken; of a sleeping bag has 6" of loft, that's 3" above you and 3" crushed below you.

6. Premium sleeping bag companies -- I am not including trading companies, merchandisers -- assume you will have a serious barrier to heat loss below you in the form of an insulating pad.

Divide the SB loft from quality down in half; and every maker of quilts here is offering the same guidance as those quality bag makers, +-5F.

7. ## Check my math

So 3" of loft would get you to 13 degrees?

Temp = (-18(3)) + 67
Temp = (-54) + 67
Temp = 13

8. according to this equation the burrow is good to 14* so its pretty close