Fill power, fill weight, hydrostatic head, MVTR and baffles, explained in plain English so you can read a parka spec sheet without guessing.
Quick take
- Fill power measures down quality, not warmth; warmth depends on fill power combined with fill weight, the total amount of down in the jacket.
- A 10,000mm waterproof rating is the minimum for a jacket to be called rainproof; below that, fabric is generally considered water-resistant.
- Breathability ratings are not standardized between brands, so compare them within one brand rather than across labels.
- For most Canadian city winters, fill weight and construction matter more than chasing an 850 fill power number.
- Dirt wears down a jacket’s DWR coating; regular cleaning and a fresh DWR treatment keep the fabric repelling water.
Winter jacket labels pile on numbers: 650 fill, 10,000 millimetres, MVTR, baffles, DWR. None of it is difficult once someone explains what each figure measures, but most product pages assume you already know. This plain-English glossary covers the terms you will see on parkas, puffers and shells, so you can compare coats on what actually matters for your climate and your budget.
Why jacket labels are hard to read
Manufacturers and fabric producers set their own waterproof and breathability ratings, with testing done in-house or at independent labs. Different labs can report different results even for two pieces of fabric from the same roll, so treat every number as a guide rather than a guarantee. A big fill power figure says nothing about how much down is in the coat, and a high waterproof rating means little if the seams are not sealed. Our guide to choosing a winter coat for Canadian winters covers the bigger decisions on fit, style and budget.
Down insulation terms
Down. The soft undercoating of duck or goose plumage, made of light clusters that trap air. That trapped air is what insulates.
Fill power. A lab measurement of down quality. One ounce of down (about 28 grams) sits in a cylinder and lofts freely, and the volume it fills in cubic inches becomes the rating. Down graded at 800 fill power expands to 800 cubic inches per ounce; 600 fill power means the same weight fills only 600. Most mainstream brands sit in the 550 to 700 range, and the jump from 700 to 800 works out to roughly 14 percent more volume per ounce.
Fill weight. The total quantity of down inside the garment, usually listed in grams or ounces. Warmth comes from fill power combined with fill weight, which is why two coats with the same fill power can feel very different.
Loft. How fully the down fluffs up and holds air. Higher fill power means larger, more resilient clusters that trap more air per gram.
Goose down vs duck down. Goose clusters are larger and can reach the highest fill power ratings. Duck down is adequate quality but rarely reaches 700 or higher.
Style tip
Fill power is a quality score, not a warmth score. A coat with 650 fill power and a generous fill weight can be warmer than a light jacket at 850, so check how much down a coat contains before paying extra for the bigger number.
Synthetic insulation terms
Synthetic insulation. Man-made fibres designed to trap air the way down does. Brands sell it under many proprietary names with no standard number to compare, so judge coats by how they describe their intended use and warmth rather than the name on the tag.
Baffle. The stitched channels or boxes that hold insulation in place so it does not shift inside the coat.
Waterproof and breathability ratings
Waterproof rating (hydrostatic head). How much water pressure a fabric withstands before moisture passes through, measured in millimetres. A 10,000mm rating means the fabric held back a 10-metre column of water before leaking. The test describes the fabric only; seams, zips, cuffs and hood design all affect how the finished jacket performs.
Water-resistant. Ratings below 10,000mm are generally considered water-resistant rather than waterproof, fine for drizzle and quick commutes but not sustained rain or wet snow.
Where common ratings land:
- 10,000mm: the minimum to be called rainproof; handles moderate rain and wet snow for short periods.
- 15,000mm: a good choice for most outdoor activity, withstanding heavy rain for extended periods.
- 20,000mm: built for prolonged exposure to heavy downpours and sustained pressure.
Breathability (MVTR). Moisture vapour transmission rate, or how much water vapour (your sweat) passes through the fabric in a set time. Higher numbers mean a more breathable fabric. Some brands use the RET scale instead, where a lower value is better. Testing methods vary widely and are not standardized across brands, so compare breathability ratings within one brand rather than between them.
PSI. A few manufacturers report waterproofing in pounds per square inch instead of millimetres. If you need to convert, 704 mm equals 1 PSI.
DWR (durable water repellent). A coating that makes water bead and roll off the outer fabric. Dirt and grime wear it down over time, so regular cleaning with a technical cleaner and a fresh DWR treatment extend a jacket’s performance.
Shell, lining and construction terms
Shell. The outer fabric layer that faces the weather. A shell jacket has no built-in insulation and relies on what you wear underneath.
Insulated shell. A shell with insulation sewn in, a one-piece solution versus a plain shell layered over warm clothes.
Seam sealing. Tape or sealant applied over stitched seams to block the needle holes. A high waterproof rating counts for little if seams are left unsealed.
Lining. The inner fabric between you and the insulation. A smooth lining slides easily over sweaters when you layer.
Fit and style terms
Parka. A longer, hooded insulated coat, typically cut to the hip or thigh, made for cold and snow.
Puffer. A coat insulated with down or synthetic fill and divided into quilted sections, from slim layers to bulky mid-length styles.
Storm flap. A flap of fabric that covers the front zipper so wind and driven snow cannot push through it.
Which terms actually matter for your climate
For most Canadian city winters, fill weight and hood design matter more than chasing an 850 fill power number, which mostly signals premium warmth for very little weight. Wet coastal snow puts the focus on waterproof ratings and seam sealing, while dry prairie cold puts insulation first. Around town, a 10,000mm rating is generally sufficient for everyday wear. What goes under the coat matters too; our guide to layering for cold weather explains how to build warmth without bulk, and a well-chosen parka earns a permanent spot in a wardrobe that works with everything.
Next step: pull up the spec sheets for the two or three coats on your shortlist and compare fill weight, waterproof rating and hood design side by side.
Your style questions
Q: Does higher fill power always mean a warmer jacket?
A: No. Fill power measures how much volume one ounce of down fills, which signals quality and loft. Warmth depends on fill power combined with fill weight, so a 650-fill jacket with lots of down can be warmer than a lighter 850-fill one.
Q: What waterproof rating do I need for a Canadian winter?
A: For everyday city wear, around 10,000mm is generally enough for snow and showers. If you spend long days out in heavy, wet conditions, 15,000mm or more offers more protection under sustained pressure.
Q: Why do two jackets with the same waterproof rating perform differently?
A: The rating describes only the fabric under lab conditions. Seams, zips, hoods, cuffs and overall construction all affect how the finished jacket keeps water out.
Q: Is goose down better than duck down?
A: Goose down has larger clusters and a higher fill power potential, so it reaches the top ratings more often. Duck down rarely reaches 700 or higher but is still adequate quality.
