Cerium LT vs Thorium AR: Which Down Jacket Is Warmer?
The Cerium LT and Thorium AR are both Arc'teryx down jackets — but they're designed for different levels of cold.
If you're trying to decide between them, this guide will help you choose the right one for your needs.
The Quick Answer
- •Cerium LT = Lightweight, packable, 850-fill down. Best for cool to cold weather.
- •Thorium AR = Warmer, heavier, 750-fill down. Best for very cold weather.
For most people: Get the Cerium LT. It's lighter, cheaper, and warm enough for most uses.
For extreme cold: Get the Thorium AR. It's significantly warmer.
Key Differences at a Glance
| Feature | Cerium LT | Thorium AR |
|---|---|---|
| Down fill | 850-fill power | 750-fill power |
| Insulation weight | Light | Heavy |
| Overall weight | ~285g (10.1 oz) | ~405g (14.3 oz) |
| Warmth | Good | Excellent |
| Packability | Excellent | Good |
| Outer fabric | Arato 10 (light) | Arato 30 (more durable) |
| Price | $379 | $399 |
| Outlet Price | $227-$265 | $240-$279 |
Down Quality vs Down Quantity
This is where it gets interesting. The Cerium LT uses higher-quality down (850-fill), but less of it. The Thorium AR uses lower-quality down (750-fill), but more of it.
Result: The Thorium AR is warmer overall, even though its down quality is lower.
Think of it this way:
- •Cerium LT: Less insulation, but higher quality = good warmth for the weight
- •Thorium AR: More insulation, slightly lower quality = more total warmth, but heavier
Warmth Comparison
The Thorium AR is noticeably warmer than the Cerium LT. Here's my experience:
- •Cerium LT: Comfortable down to ~25°F (-4°C) standing around
- •Thorium AR: Comfortable down to ~10°F (-12°C) standing around
If you need a jacket for seriously cold weather, the Thorium AR is the clear winner. For most three-season use, the Cerium LT is plenty warm.
Weight & Packability
- •Cerium LT: ~285g — packs to the size of a Nalgene bottle
- •Thorium AR: ~405g — packs to about twice the size of the Cerium LT
If you're counting grams or need a jacket that packs small, the Cerium LT wins. The Thorium AR is noticeably heavier and bulkier.
Durability
The Thorium AR is more durable than the Cerium LT.
- •Cerium LT: 10D Arato face fabric — very light, somewhat delicate
- •Thorium AR: 30D Arato face fabric — more durable, can handle more abuse
If you're hard on your gear, the Thorium AR is the better choice. If you're careful with your gear, the Cerium LT is fine.
Price & Outlet Value
| Cerium LT | Thorium AR | |
|---|---|---|
| Full Price | $379 | $399 |
| Typical Outlet (30% off) | $265 | $279 |
| Good Outlet (40% off) | $227 | $239 |
The prices are similar, with the Thorium AR being slightly more expensive. At outlet prices, both are excellent values.
Which One Should You Buy?
Get the Cerium LT if you:
- •Want a lightweight, packable down jacket
- •Need warmth for cool to cold weather (25°F and up)
- •Value weight and packability over maximum warmth
- •Travel a lot and need something that packs small
- •Want the highest-quality down
Get the Thorium AR if you:
- •Need maximum warmth for very cold weather
- •Live in a cold climate
- •Want a more durable jacket
- •Don't mind the extra weight and bulk
- •Are willing to sacrifice packability for warmth
Our Recommendation for Most People
Get the Cerium LT. It's lighter, more packable, and warm enough for most uses. It's the more versatile jacket.
But if you live in a cold climate and need something for standing around in freezing temperatures: Get the Thorium AR. The extra warmth is worth the weight.
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