The CS:GO Trade Up Contract requires 10 skins of the same rarity to be exchanged for 1 skin that is of one higher rarity with the outcomes being chosen 'randomly' from one of the inputted collections or cases.
You can't use both StatTrak™ and non StatTrak™ skins in one Trade Up Contract.
Souvenir skins cannot be used in tradeup contracts.

(OLD) To calculate the float of the each outcome, the formula is:

OutputFloat = (MaxFloat - MinFloat) * AVG + MinFloat.

AVG = The average float of the 10 input skins.
MinFloat = MinFloat of possible reward.
MaxFloat = MaxFloat of possible reward.

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The AK-47 | Redline float ranges from 0.10 (MinFloat) to 0.70 (MaxFloat).

With the calculations, the FN Redline is impossible to get as the lowest float a redline can be is 0.10 which is MW.
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The AK-47 | Fire Serpent float ranges from 0.06 (MinFloat) to 0.76 (MaxFloat), which makes AK-47 | Fire Serpent available in all conditions.

This makes the FN Fire Serpent extremely hard to craft as the AVG Float needs to be extremely low. This is why you might see some YouTubers and Streamers craft a MW Fire Serpent when they are aiming for the FN condition.

Finding the correct floats for items are sometimes really hard to find. Here are a list of some ways to find them:

• Create Buy Orders
  
• Snipe them through refreshing for new listings/revisiting the pages every hour or so
  
• Trading/Buying from 3rd party sites such as Skinbaron, Skinport, cs.money etc

The new theory of how trade up outcomes are determines are based on the number of available skins from each collection. This sounds really confusing at first but once you get your head around it, its relatively easy to understand.

This tradeup example consists of 6 FT overpass skins and 4 FN Train skins.

As you can see, the train skins have only 2 possible outcomes and in this trade up we are using 4 of these train filler skins.
The Overpass skins on the other hand have 3 possible outcomes and we are using 6 of them in the trade up above.As there are 4 train skins in this trade up and we know there are 2 only possible outcomes, we multiply the two numbers together (4 x 2 = 8). The 6 overpass skins used in this trade up only have 3 possible outcomes so we multiply them as well (6 x 3 = 18).

Next add the two totals together (8 + 18 = 26).

Now we calculate the percent chance to get a skin from the collection used in the trade up.
For the outcomes in this trade up, the chance we get a train outcome is 8/26 or 30.77% and the chance we a skin from the overpass collection is 18/26 or 69.23% chance.

To calculate the individual percent chance to get a skin we divide the collections outcome by how many outcomes there are.
Train is 8/2 (only two Train outcomes) = 4/26 for each
Overpass is 18/3 (only three possible Overpass outcomes) = 6/28 for each Overpass outcome.

Therefore:
4/28 (15.38%), 4/28 (15.38%) for both Deagle and the Sawed Off from Train
6/28 (23.08%), 6/28 (23.08%), 6/28 (23.08%) respectively for the XM, Scout an CZ.

If you are still unsure, checkout Heyzues' video.
0:41 to 1:44

*Basically the trade up prefers the collection with more outcomes.

The contract only allows 10 skins from the same rarity. For example: 10 Mil-Spec skins can only be crafted into 1 Restricted skin.
↓ Consumer Grade - Grey
↓ Industrial Grade - Light blue
↓ Mil-Spec - Blue
↓ Restricted - Purple
↓ Classified - Pink
Covert - Red

There are many sites that have a trade up calculator but by far the easiest one to use is TradeUpSpy[www.tradeupspy.com].


Advantages of TradeUpSpy:

• The site is completely free to use and does not need to be paid for unless you want premium.
  
• It is really easy to link your steam inventory and search for the input skins for the trade up.
  
• The site accounts for a wide range of currencies if not all for people to choose from.
  
• The steam tax of 15% has been taken into account for the outcomes of the trade up.
  
• The site provides 3 free examples of trade ups which can be used by the users.

For more information, go to: https://www.tradeupspy.com/documentation

To look at previously completed trade ups, go to your Item Inventory > More > View Inventory History.

ST Prisma 2 Trade Up:
4x FN Glove Skins, 6x MW Prisma 2 Skins
AVG Float <0.069
Made $16 Profit
[Update] Less profitable now as the case has become more common.
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Norse Collection Trade Up:
2x WW Norse Skins, 8x FN Italy Skins
AVG Float <0.138 (Norse outcomes end floats are 0.069 = FN)
[Update] Not profitable anymore as the Norse WW input skins have risen in price.
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Canals Collection Trade Up:
3x FT Canals Skins, 7x FN 2018 Nuke Skins
AVG Float <0.069
Made $8 Profit
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HIGH RISK 9% Bulldozer Trade Up:
1x FN Chop Shop Skins, 9x FN Lake Skins
AVG Float <0.011 (wasn't using TradeUpSpy [www.tradeupspy.com]at the time so i'm not quite sure about the avg float)
Made $130 Profit
[Update] Not as profitable anymore as the SG was nerfed.

Here are a few examples of profitable trade ups you can do with the new Fracture case.

(Note - all prices are in Australian Dollars)

Stat-Trak Mil-Spec Fracture Case Trade Up 1:
4x FN Gloves Skins, 6x MW Fracture Skins
AVG Float <0.069

Stat-Trak Mil-Spec Fracture Case Trade Up 2:
6x FT Fracture Skins, 4x MW Breakout Skins
AVG Float <0.139

Restricted Fracture Case Trade Up:
10x FT Fracture Skins
AVG Float <0.199

Stat-Trak Restricted Fracture Case Trade Up 1:
10x ST FT Fracture Skins
AVG Float <0.199

Restricted Fracture Case Trade Up 2:
9x MW Fracture Skins, 1x FT Fracture Skin
AVG Float <0.0933

Stat-Trak Restricted Fracture Case Trade Up 2:
10x ST MW Fracture Skins
AVG Float <0.0933

↑ ALL TRADEUPS ABOVE ARE FROM 9 OCTOBER 2020

Special thanks to:
Misu @ TradeUpSpy [www.tradeupspy.com] for letting me use your site!

If this guide was any help to you, feel free to donate!

Feel free to use my Referral Code [www.tradeupspy.com]on TradeUpSpy which will give you an extra 2 days of premium for each month purchased!

Noting all the recent hype and volatility of skins in the market, i recommend you take advantage of this and try make some profit while you can.

Whether your goal is to increase steam wallet funds or make money, this is a low effort and almost risk free way (caution: still has risk) to profit.

2024 Overpass Collection Tradeup
4x FN, 6x MW Overpass Collection Skins
AVG Float <0.0823
https://www.tradeupspy.com/calculator/share/eaze/undefined/false/5/0.035,0.035,0.035,0.035,0.12,0.1,0.12,0.12,0.1,0.1/8380,8380,8380,8380,8380,8380,8380,8380,8380,8380/8375,8377,8376/3.5,3.5,3.5,3.5,1.62,1.62,1.62,1.62,1.62,1.62/34.29,34.24,32.71

Radiant Collection Tradeup
10x FT Radiant Collection Skins
AVG Float <0.199
https://www.tradeupspy.com/calculator/share/eaze/undefined/false/6/0.2,0.2,0.2,0.2,0.2,0.2,0.2,0.2,0.2,0.19/9115,9115,9115,9115,9115,9115,9115,9115,9115,9115/9110,9107,9106,9105,9109,9108/0.21,0.21,0.21,0.21,0.21,0.21,0.21,0.21,0.21,0.21/3.59,3.46,3.53,3.62,3.57,3.57

Boreal Collection Tradeup
10x MW Boreal Collection Skins
AVG Float <0.0933
https://www.tradeupspy.com/calculator/share/eaze/undefined/false/6/0.093,0.093,0.093,0.093,0.093,0.093,0.093,0.093,0.093,0.093/9145,9145,9145,9145,9145,9145,9145,9145,9145,9145/9132,9133,9134,9135,9136/0.72,0.72,0.72,0.72,0.72,0.72,0.72,0.72,0.72,0.72/23.85,9.28,4.72,4.67,4.08

Ascent Collection Tradeup
10x FT Ascent Collection Skins
AVG Float <0.199
https://www.tradeupspy.com/calculator/share/eaze/undefined/false/5/0.2,0.2,0.2,0.2,0.2,0.2,0.2,0.2,0.2,0.199/9163,9163,9163,9163,9163,9163,9163,9163,9163,9163/9159,9160/1.15,1.15,1.15,1.15,1.15,1.15,1.15,1.15,1.15,1.15/32.51,21.15

Fever CaseTradeup
5x FN Any cheap (e.g. recoil, revolution, fever), 5x MW Fever Case Skins
AVG Float <0.699
https://www.tradeupspy.com/calculator/share/eaze/undefined/false/4/0.1,0.1,0.1,0.1,0.1,0.04,0.04,0.04,0.04,0.039/9067,9067,9067,9067,9067,7044,7044,7044,7044,7044/7037,7050,7051,9064,9063,9062/1.28,1.28,1.28,1.28,1.28,2.84,2.84,2.84,2.84,2.84/22.14,21.7,17.93,65.6,44.48,33.77

Fracture Case Tradeup
10x FT Fracture Case Skins
AVG Float <0.199
https://www.tradeupspy.com/calculator/share/eaze/undefined/false/4/0.199,0.199,0.199,0.199,0.199,0.199,0.199,0.199,0.199,0.199/877,877,877,877,877,877,877,877,877,877/872,873,874/0.31,0.31,0.31,0.31,0.31,0.31,0.31,0.31,0.31,0.31/6.44,5.82,5.35

Dreams and Nightmares CaseTradeup
10x MW Dreams and Nightmares Case Skins
AVG Float <0.092
https://www.tradeupspy.com/calculator/share/eaze/undefined/false/5/0.092,0.092,0.092,0.092,0.092,0.092,0.092,0.092,0.092,0.092/5680,5680,5680,5680,5680,5680,5680,5680,5680,5680/5678,5679,5676,5675,5677/0.14,0.14,0.14,0.14,0.14,0.14,0.14,0.14,0.14,0.14/4.68,3.32,2.93,2.83,0.73