What Is Fill Power (FP)?

When comparing down quilts, jackets or sleeping bags, you’ll often see the term “Fill Power (FP)” — but what does it actually mean?
In simple terms, Fill Power measures the loft or “fluffiness” of down insulation, showing how much space one ounce of down occupies when fully expanded. It’s the clearest indicator of warmth, quality, and long-term performance.

Frequently Asked Questions

What does Fill Power measure?
Fill Power measures how many cubic inches of space one ounce of down fills when fully lofted. For example, 800FP down expands to fill 800 cubic inches per ounce, while 600FP down fills 600 cubic inches. The higher the number, the warmer, lighter, and more compressible the product.

How is Fill Power tested?
It’s measured in a laboratory setting: one ounce of down is placed in a cylinder, a weight is applied, and the resulting volume is recorded. This ensures accurate comparison across products and brands.

What affects Fill Power quality?
Higher Fill Power comes from larger, more mature down clusters that trap more air and rebound better after compression. These clusters deliver greater insulation and durability — qualities found in premium down used by Supreme Quilts.

Is higher Fill Power always the best choice?
Not always. While higher FP offers superior insulation, the right option depends on climate, personal comfort, and price. For example, a 700FP quilt might suit Melbourne winters, while a 550FP quilt is ideal for Queensland nights.

What’s the difference between Fill Power and Fill Weight?
Fill Power reflects the quality of the down, while Fill Weight measures the quantity used. A lighter, high-FP quilt can perform just as warmly as a heavier, lower-FP one — depending on design and construction.

Key Features to Consider

• Warmth-to-Weight Efficiency: Higher FP = more warmth with less bulk.

• Down Quality: Mature goose down generally delivers better FP.

• Shell Fabric: Fine, tightly woven fabrics help maintain loft and breathability.

• Balance of Fill Power and Weight: Warmth depends on both.

• Intended Use: Choose based on local climate and lifestyle.

• Ethical Sourcing: Look for Responsible Down Standard (RDS) certification.

How Fill Power Works and What to Consider When Buying

Fill Power (FP) is a precise measure of down quality, showing how many cubic inches of space one ounce of down occupies when fully expanded. The higher the Fill Power, the more air it traps, providing better warmth-to-weight efficiency — making your quilt warmer and lighter.

Measurement:
In lab testing, one ounce of down is placed in a cylinder, a weight is applied, and the volume it occupies is recorded. For example, 800FP down fills 800 cubic inches per ounce, while 600FP fills 600 cubic inches. This process ensures every Fill Power rating is scientifically consistent across the industry.

Quality:
Higher Fill Power values indicate larger down clusters, typically from older, more mature birds. These clusters are more effective at trapping air, which enhances insulation and loft. They also tend to be more resilient — meaning your quilt will retain its fluffiness for years to come.

Performance:
Because high-FP down provides more warmth per ounce, manufacturers can use less material while maintaining excellent insulation. That’s why 800FP quilts feel light and compressible, yet deliver premium warmth compared to lower-FP alternatives.

Fill Power vs. Fill Weight:
It’s important to remember that Fill Power shows quality, while Fill Weight shows quantity. A high-FP quilt isn’t automatically warmer unless it also contains enough down. For example, a 700FP quilt with high fill weight may outperform an 800FP quilt with low fill weight.

Balancing Factors:
Choosing a quilt involves trade-offs between fill power, fill weight, and cost. A lighter 800FP quilt may feel luxuriously airy, while a heavier 600FP version might offer similar warmth for less money. The best choice depends on your budget, climate, and preference.

Best Use Cases:
High Fill Power is perfect for performance use, such as travel or camping, where weight and packability matter. For everyday home comfort, a mid-range FP (650–750) quilt provides superb warmth, softness, and value.

Understanding Fill Power in Down Quilts

Fill Power defines how effectively down traps heat and provides insulation. The higher the FP, the more air one ounce of down can hold — meaning greater warmth and comfort for less weight.

For example, Supreme Quilts often use down in the 700–850FP range, ensuring an ideal balance of softness, resilience, and thermal performance. Understanding this number helps you pick a quilt that performs exactly how you need it to — no guesswork, no disappointment.

Warmth-to-Weight Ratio

This is where Fill Power truly matters. A 600FP and an 800FP quilt can offer similar warmth, but the higher FP option achieves it with less down. That means lighter bedding, less bulk, and easier handling.
For colder states like Victoria and Tasmania, go for 750FP or higher. For warmer regions, stick to 550–650FP for optimal comfort.

Loft and Softness

Loft refers to the height and fluffiness of the down. It directly reflects Fill Power — the higher the FP, the plusher and softer the feel.
Larger clusters create a luxurious, cloud-like texture and recover better after compression. To maintain loft, air your quilt regularly and store it uncompressed. Premium down continues to rebound beautifully even after years of use.

Climate Suitability

Australia’s climate varies widely — and so should your Fill Power choice.
In cooler areas, higher FP provides essential insulation. In warmer zones, a lighter FP offers comfort without overheating.

If you’re unsure which FP suits your needs, contact us for tailored guidance based on your region and temperature preferences.

Durability and Resilience

High-Fill Power down lasts longer because its clusters are larger, stronger, and less prone to breaking down.
When paired with quality cotton casing and baffle-box stitching, it stays evenly distributed and warm for years.
Low-FP fills may flatten or clump over time — while premium FP down maintains its structure and bounce-back, season after season.

Breathability and Moisture Control

Higher FP means fewer, larger clusters, which improves airflow and moisture regulation.
This natural breathability keeps you warm yet dry, especially in humid climates.
Paired with a light cotton or German Batiste shell, high-FP quilts provide a balanced sleeping temperature for consistent comfort.

Value and Craftsmanship

While FP defines the quality of insulation, craftsmanship defines how that insulation performs.
Strong stitching, baffle-box construction, and premium materials ensure down stays evenly spread.

At Supreme Quilts, expert tailoring meets ethical sourcing, producing quilts that are luxurious, long-lasting, and responsibly made.
Each design is precision-filled for perfect warmth and consistency — a blend of science and art that stands the test of time.

Bringing It All Together

Fill Power isn’t just a number — it’s a reflection of quality, warmth, and care.
By understanding FP, you can confidently select a quilt that suits your climate, comfort level, and lifestyle.

Balance Fill Power, Fill Weight, and construction quality to achieve the best sleep possible.
Whether you want light, airy bedding or deep winter warmth, the right FP level ensures lasting comfort and long-term value.

Investing in the right down product means investing in better rest, durability, and sustainable craftsmanship — exactly what sets Supreme Quilts apart.