BEDDING GUIDE · 23 OCTOBER 2026 · BY LAVE STUDIO

Silk duvet fill weight: what 150, 250 and 400 g/m² mean

A filling weight tells you how much silk is spread across the insert. It helps you compare options, but it is not the weight of the finished duvet or a tested warmth rating.

What does g/m² mean?

The unit means grams per square metre. A 250 g/m² insert contains a calculated 250 grams of filling for each square metre of its area. It describes the filling alone; the outer shell adds to the weight you lift onto the bed.

Lave’s mulberry silk duvet insert has three filling options: Light at 150 g/m², Medium at 250 g/m² and Warm at 400 g/m². The filling is long-filament mulberry silk, with a cotton outer shell. A removable duvet cover is separate.

Calculate the silk in your size

Multiply the width and length in metres, then multiply that area by the chosen fill weight. For a 200 × 200 cm insert:

2 m × 2 m = 4 m². At 250 g/m², that gives a calculated 1,000 g of silk filling.

Calculated silk filling for a 200 × 200 cm insert
Lave option	Filling per m²	Silk filling
Light	150 g	600 g
Medium	250 g	1,000 g
Warm	400 g	1,600 g

These are calculations from the selected dimensions and filling density, not scale measurements of finished inserts. They exclude the cotton shell and your duvet cover.

Why a larger insert contains more silk

At the same 250 g/m², a 260 × 220 cm insert has an area of 5.72 m² and a calculated silk filling of 1,430 g. That is more silk than the 200 × 200 cm example because there is more area to fill. The filling per square metre has not increased.

When comparing two sizes, compare their g/m² figures as well as their total filling weights. A higher total weight can simply mean a larger duvet. Match the measurements to your cover before deciding how much filling you want.

Why grams cannot give you a TOG rating

TOG concerns thermal resistance; filling mass is a different measurement. In its independent duvet testing, Hong Kong’s Consumer Council measured thermal resistance and duvet weight separately, using BS 4745 for the thermal-resistance measurement.

We do not publish a tested TOG rating for Lave’s inserts. You should not read 250 g/m² as a particular TOG, or assume that a silk insert and a down duvet with the same filling weight will feel alike. The Council’s results concern the products it tested, not Lave’s range.

Choose the amount for how you sleep

Light, 150 g/m²: a starting point if you prefer less filling or often push a heavier duvet aside.
Medium, 250 g/m²: more filling per square metre if Light sounds too slight for your preference.
Warm, 400 g/m²: the most filling in this range, for people who prefer more substantial bedding.

These are relative choices, not room-temperature bands. More filling is not a quality grade, and the heaviest option is not automatically the best choice. Consider your usual bedroom conditions, removable cover and personal preference together.