Fill Power Comparison: 800 vs 850 vs 900 vs 950

By topquilt.com · Updated Oct 21, 2026 · 7 min read

This fill power comparison puts numbers on the 800 vs 850 vs 900 vs 950 question. Fill power is the volume, in cubic inches, that one ounce of down occupies under standard lab conditions. Higher fill power means each ounce lofts more, so a maker needs fewer ounces to build a quilt of the same thickness. Below we work through the math so you can judge whether an upgrade is worth the price.

For background on how fill power is measured, see down fill power explained.

The formula

The relationship is simple:

• Loft volume (cu in) = fill weight (oz) × fill power
• Fill weight needed = target volume ÷ fill power

A quilt maker designs a quilt to a target loft (determined by baffle height and dimensions) and chooses the fill weight to hit it. Upgrading fill power lowers the ounces needed; the warmth stays the same. Makers also add some overfill above the theoretical amount, but the ratios hold.

Fill power comparison: the percentages

Each 50-point step saves a bit less than 6% of the down weight — and only the down weight, not the fabric, zipper or straps.

Worked example: a 20°F quilt

Suppose a 20°F regular quilt needs about 12,800 cubic inches of loft. At 800 FP, that's 16 oz of down. Here's what the other fill powers require:

Going from 800 to 950 saves about 2.5 oz — roughly 11% of the total quilt weight in this example.

Worked example: a 40°F summer quilt

A 40°F quilt needs far less loft — say about 6,400 cubic inches, or 8 oz of 800 FP down.

On warm-weather quilts the savings shrink to about an ounce. That makes premium fill hard to justify for summer use unless you're optimizing every gram.

Worked example: a 0°F winter quilt

A 0°F quilt might need about 19,200 cubic inches, or 24 oz of 800 FP down.

The colder the quilt, the more down it holds, and the more a fill power upgrade saves. This is where 950 fill earns its keep. See best winter top quilts.

Packed size

Higher fill power down also compresses smaller because there is less of it. The packed volume difference tracks the weight difference roughly — expect a 950 FP quilt to pack noticeably but not dramatically smaller than an 800 FP version. Fabric and baffles take up space too, so the effect is diluted.

A rough worked estimate: if a 20°F 800 FP quilt packs comfortably into about 10 liters, the down accounts for most of that volume. Cutting the down by about 16% at 950 FP shrinks the down's share by the same proportion, so the quilt might pack into roughly 8.5–9 liters. That's about the difference between a stuff sack that fills the bottom of your pack and one that leaves room for a cook kit beside it.

Hammock vs ground: the savings double

Ground sleepers buy one quilt; hammock campers buy two — a top quilt and an underquilt — and both are usually down. Using the 20°F example above for each piece:

Five ounces is a meaningful saving, but the upgrade cost also doubles. Many hammock campers split the difference: a premium-fill top quilt that travels with them on ground trips too, and a value-fill underquilt. See the hammock top quilt guide.

Wet weather: does fill power change the picture?

Because a 950 FP quilt holds less down, it has less margin: if humidity costs both quilts the same percentage of loft, they lose warmth equally. What changes is recovery and treatment. In wet climates, prioritize treated down and a DWR shell over the jump from 850 to 950 FP, and plan to air the quilt whenever the sun comes out. If you face days of rain with no chance to dry gear, synthetic may serve better than any fill power; see down vs synthetic quilts.

Cost per ounce saved

Price premiums for higher fill power vary by maker and fluctuate with the down market. A useful way to evaluate an upgrade is to divide the price difference by the ounces saved. For example, if upgrading a 20°F quilt from 850 to 950 FP costs an extra $100 and saves about 1.6 oz, you're paying around $60 per ounce. Compare that with other ways to save weight in your kit, such as a lighter pad or shelter, before deciding.

Budget examples

Here's how the decision plays out at different budgets:

• Tight budget ($ tier): a lower fill power quilt such as the Paria Thermodown gets you into quilts for far less, accepting a few extra ounces. See best budget top quilts.
• Value cottage ($$ tier): economy lines such as the Hammock Gear Economy Burrow use 800-range fill, often the best warmth per dollar.
• Standard cottage ($$$ tier): 850 FP custom quilts like the Burrow or Revelation are the most common choice for thru-hikers.
• Premium ($$$$ tier): 950 FP builds and very cold ratings, where the per-ounce savings are largest. See best ultralight quilts.

Common mistakes

• Upgrading fill power on a summer quilt where it saves well under an ounce and a half.
• Choosing 950 FP in a narrower width to save weight, then sleeping cold from drafts.
• Comparing quilts by fill power alone instead of rating and fill weight.
• Skipping overfill to afford higher fill power. For cold sleepers, an extra ounce of 850 FP often does more than 950 FP.

Fill power vs other ways to save weight

Before paying for 950 fill, consider where else the same ounces might come from:

Approximate figures; they vary by quilt size and maker. The point is that fill power is one lever among several. Pick the ones that cost you the least comfort. See quilt shell fabrics and width and length sizing.

Lower fill powers: 600–750

Budget quilts sold through big retailers often use 600–750 fill power. Running the same math, a 20°F quilt needing 12,800 cubic inches would take about 21 oz of 600 FP down or 18.3 oz of 700 FP down — 5 oz and 2.3 oz more than 800 FP. That's a real penalty for long-distance hikers, but for a first quilt or hammock camping close to the car, it's often a sensible way to save a lot of money. See best budget top quilts.

Does higher fill power hold up in humidity?

All down loses loft when it absorbs moisture, regardless of fill power. Some hikers believe the finest, highest fill power down is more sensitive to humidity; there's little rigorous public data either way. What clearly helps is a water-resistant treatment, a breathable but DWR-coated shell, and drying the quilt in the sun when you can. See hydrophobic down.

What fill power doesn't tell you

• Warmth. A 950 FP quilt isn't warmer than an 800 FP quilt of the same rating. Look at the rating and fill weight. See fill weight and overfill.
• Testing standard. US and European test methods for fill power differ, and numbers aren't always directly comparable between markets.
• Species. Duck and goose down perform the same at the same fill power. See duck vs goose down.
• Moisture resistance. That depends on treatment; see hydrophobic down.

Verdict: which fill power should you choose?

Choose 800 fill power if…

• You want the best value and don't mind an extra ounce or two.
• You'd rather spend the savings on overfill, width or a better pad.

Choose 850 fill power if…

• You want the common cottage-quilt sweet spot of weight and price.
• You want a quilt for three seasons that packs small.

Choose 900 fill power if…

• You want a meaningful weight saving without paying the highest premium.

Choose 950 fill power if…

• You're an ultralight hiker optimizing every ounce.
• You're buying a 10°F or 0°F quilt where the savings are largest.
• Packed size is tight in a small pack.

For the lightest quilts on the market, see best ultralight quilts; for overall weight guidance, see the quilt weight guide and the top quilt buying guide.