Light duvet: What is the right filling weight?

A lightweight duvet is an imprecise term. It describes neither material nor warmth class—but rather the fill weight. And that is precisely the crucial factor that determines whether a summer duvet is cool enough for you or if it will still be too warm. This guide clarifies which fill weight suits which room temperature, why 250 g is not always 250 g, and how to find the right duvet for your sleeping style.

What "lightweight duvet" really means

A duvet is called "lightweight" if it contains less filling material compared to an all-season or winter duvet. The warmth class is based on this fill weight: the less filling, the less trapped air—and air is the actual insulator. The material plays a role (down insulates better than cotton), but the fill weight is the dominant factor.

The designations in trade are inconsistent. "Extra light," "summer," "light quilt"—these can mean anything and nothing. The only hard number is the fill weight in grams, ideally for a 135x200 format as a reference. Manufacturers who do not specify this usually do not want to disclose their weight—often because it is lower than suspected.

The three relevant fill weight classes in summer

For a 135x200 duvet, three classes have been established, which almost all reputable manufacturers specify. For larger formats, weights scale proportionally to the area.

250 g — the extra-light class

250 g filling for a 135x200 duvet is the lightest option on the market. This results in a fill weight per square meter of about 93 g—very little. The duvet is almost imperceptible, conforming to the body without weighing it down. For very hot summer nights or for people who generally sleep warm, this is the right choice. If in doubt, for room temperatures of 25+ degrees.

400 g — the standard summer class

400 g filling is the standard for summer duvets in German-speaking countries. A good balance for summer nights between 18 and 24 degrees room temperature. The duvet has enough substance to feel warm, but quickly wicks away moisture. For single sleepers with an average sleeping climate, this is usually the right choice.

600 g — the transition to the all-season duvet

600 g is already a lightweight all-season duvet. It is suitable for cooler summer nights, air-conditioned bedrooms, or those sensitive to cold. Those who never sweat but get cold easily are often better off with a 600 g variant than with a true summer duvet. This is the transitional area between summer and all-season.

Comparison table: Fill weight to room temperature

Fill weight (135x200)	Room temperature	Sleeper type	Season
250 g (Extra light)	above 24 °C	Hot sleepers, sweaters	Mid-summer
400 g (Summer Standard)	18–24 °C	Average sleeping climate	Early summer to late summer
600 g (Light all-season)	16–20 °C	Sensitive to cold	Transition, air-conditioned room
800–1000 g (All-season)	14–18 °C	Normal to cold-sensitive	All year except mid-summer
1200+ g (Winter)	below 16 °C	Cold sleepers, cold rooms	Winter

Why 250 g is not always 250 g

This is where most advice stops. Fill weight is a number on the label—but the warmth effect depends on two other factors: material and fill power.

Material: Down vs. Cotton vs. Microfiber

Down has a significantly higher fill power per gram than cotton or polyester. This means: 250 g of pure down traps more air than 250 g of cotton. So, the down duvet is warmer at the same fill weight—with a lower inherent weight. This sounds paradoxical but is why down duvets are so popular: great warmth performance with minimal weight.

Cotton fillings are heavier, more breathable, but less thermally efficient. 400 g of cotton is roughly equivalent to 300 g of down in terms of warmth. Primaloft Bio microfiber lies in between: it insulates better than cotton, but not as well as down.

Fill Power in Down

Fill power measures how much volume a certain amount of down occupies. High-quality European goose down has a fill power of 700–800 cuin (cubic inches per ounce). Cheap duck down from Asia is around 500–600. This means: 400 g of high-quality down warms significantly more than 400 g of cheap down because more air is trapped.

At BEFA, only Downpass-certified European goose down is used. This explains why our 400 g summer duvet is often perceived as warmer than a 500 g variant from a discount store: the fill power is higher.

Fill weight for other duvet formats — the conversion factor

Manufacturer specifications almost always refer to 135x200. If you buy a larger duvet, you need to scale it so that the thermal performance per area remains the same.

• 135x200 (Reference) — 2.7 m²
• 155x220 (+25%) — 3.4 m²
• 200x200 (+48%) — 4.0 m²
• 220x240 (+96%) — 5.3 m²

So, if a 400 g summer duvet for 135x200 is considered right, you'll need about 500 g for 155x220 and about 600 g for 200x200. Reputable manufacturers automatically scale this—cheaply manufactured duvets often have the same fill weight across all formats, which means: in larger formats, they are cooler, in smaller formats, they are warmer. BEFA adjusts the fill weight individually per format.

What your room temperature really is (not what you think)

Most people underestimate how cold their bedroom actually gets at night. 22 degrees during the day doesn't mean it's still 22 degrees at night—the temperature in an unheated room usually drops by 3–5 degrees. This means: if you buy a 400 g duvet for a 22-degree room temperature, you'll be sleeping at 17–19 degrees at night—and you'll be cold.

Recommendation: Measure the temperature at 3 AM, not at 10 PM. A simple digital thermometer for 10 euros is sufficient. If you want a general orientation:

• Ground floor bedroom with good insulation: approx. 19–21 °C at night
• Attic in summer: approx. 24–28 °C at night
• Old building with single-pane windows: approx. 17–19 °C at night
• Air-conditioned room: approx. 20–22 °C at night

Examples: Which BEFA summer duvet for which situation

Attic at 27 degrees — Tencel or pure down 250 g

Heat accumulates in the attic. Anyone sleeping under a 400 g duvet there will sweat through the night. Recommendation: 250 g filling with a cooling cover. The Pure Down Duvet 100% Down Summer offers this extra-light filling in high-quality European goose down.

Average bedroom at 20 degrees — Primaloft Bio 400 g

For typical bedroom use in German summers, the Clima Primaloft Bio Summer Duvet in the standard summer class is well-suited. Washable, allergy-friendly, without animal components. The fill quantity is designed for normal bedroom temperatures.

Cool bedroom at 17 degrees — Tencel All-Season 600 g

If you still get cold in summer—poorly insulated room, air-conditioned room, sensitivity to cold—you shouldn't opt for a summer duvet, but rather a lightweight all-season duvet. The Tencel All-Season Duvet 90% Goose Down would be the better choice here. Details can be found in the guide All-Season Duvet: Advantages and Use Cases.

How fill weight behaves over the years

A summer duvet does not lose its fill weight, but its fill power—and that's a difference. Down loses volume after five to ten years because the fine barbs slowly break off. The fill weight remains the same, but the amount of air per gram decreases. The duvet feels flatter and warms less.

This means: if after 8 years you feel that your summer duvet is no longer warm enough, even though it was never broken, you are experiencing exactly this phenomenon. Remedy: wash it (allows the down to fluff up again) or, with more severe material fatigue, professional re-filling. Care significantly influences its lifespan—detailed in the guide Washing a down duvet.

Common mistakes when choosing fill weight

• Bought too light out of summer fear: If you panic about hot nights and immediately grab a 250 g duvet, even though your bedroom is only 19 degrees, you'll be cold for half the night and curl up in the morning.
• Evaluated fill weight without material context: 400 g of microfiber is not as warm as 400 g of down. If you compare material classes, you need to convert.
• Standard fill weight for a larger duvet: If you buy a 200x200 with 400 g (which would be the 135x200 quantity), you get a spatially cooler duvet—often without realizing it.
• Only looking at the price: Cheap down with 500 cuin fill power warms as much at 500 g as 350 g of good goose down. If you only pay attention to weight, you pay more and get less.
• Not planning a trial phase: Summer duvets need to be tested for two weeks in the real bedroom—the fill quantity cannot be assessed in the store.

The sleeper type: Hot and cold sleepers

In addition to room temperature, your individual metabolism is crucial. Statistically, women sleep slightly cooler than men (lower core body temperature), older people feel the cold more than young people, and physically active individuals often have more inherent warmth than couch potatoes. These are not clichés but physiology.

Anyone prone to sweating at night needs not only less fill weight but also a material that actively wicks away moisture. Tencel, linen, and pre-washed cotton are better here than classic satin covers. Detailed in the guide Sweating at night: Which duvet helps.

BEFA summer duvets in fill weight overview

At BEFA, all summer duvets are marked with transparently stated fill weight. The fill quantity is individually adjusted per format—a 200x200 contains more filling than a 135x200, so that the thermal performance per square meter remains identical.

• Extra light (250 g for 135x200): Pure Down Duvet Summer
• Summer Standard (400 g): Tencel Goose Down 90% Summer, Primaloft Bio Summer
• Light all-season (600 g): Tencel All-Season 90%, Clima Primaloft Bio All-Season

All variants can be found in the Summer Duvet Collection and the Primaloft Collection. For customers who want to consider material and fill weight together, the guide Summer Duvet Material in Detail is recommended.

Quick decision aid: Which fill weight for you

• You sweat a lot at night, your room is over 22 °C → 250 g (Extra light)
• You sleep moderately warm, room 18–22 °C → 400 g (Summer Standard)
• You get cold quickly, room under 20 °C → 600 g (Light All-Season)
• You are female, cold-sensitive, slender → choose one class higher
• You are male, warm-blooded, athletic → if in doubt, choose one class lower
• You are buying for 200x200 or 155x220 → increase fill weight by 25–50%

What BEFA does differently

We categorize our summer fill weights into three classes: 250 g (tropical nights), 400 g (standard summer), 600 g (cool nights and transition period). This principle is based on our own measurements in production—we check the thermal performance at 18 °C and 24 °C room temperature with a surface thermometer. Blanket statements like "summer duvet = 300 g" ignore that a 300 g duvet in a 17 °C bedroom is simply too cold.