Some information that will assist you with researching or buying a down sleeping bag to suit your needs...

The quality of down is measured using two criteria: its Fill Power and Down Content.

The Fill Power of down measures the ‘strength’ of the down, or its ability to resist compression, and how well it can loft. A Fill Power rating of 750+ indicates that a 30g sample of down will occupy 750 cubic inches when subjected to a standard compression force. The higher the Fill Power the better the down. Downs do not all perform equally. Bags with down of a higher fill power give more loft and warmth for the same weight.

Note: The US system of measuring Fill Power differs from the European system so, when comparing qualities you need to take into consideration that the US system will appear to give a better Fill Power, for example:560+(EU) = 610+(US), 660+(EU) = 725+(US) and 750+(EU) = 850+(US).

Down is graded according to the mix of pure down clusters and small feathers. This is represented as a percentage ratio, for example: 85:15, 90:10 or 96:4.

Down which is quoted as being 85:15 indicates that it comprises 85% down cluster and 15% small feather.

Most 80:20 or 85:15 percentage ratio down sleeping bags tend to use high quality duck down which, although will not give you quite the same performance as higher ratio bags, will be kinder to your pocket and provide adequate performance from summer to three season use.

Down sleeping bags with a 90:10, 92:8 and 96:4 percentage ratio always use pure white goose down giving you absolutely the best performance you could possibly expect.

The construction utilised in a down sleeping bag is as important as the down filling itself. Optimal sizing of channels and down fill is paramount to avoid cold spots and low thermal efficiency.