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We all know crew proficiency is important, but few of us know exactly by how much. Therefore, I have created this handy guide that not only explains how it works, but goes on to do all the calculations for you [I'm a mathematics major, so computation is a pleasure ]

This also aims to answer the question of whether Brothers in Arms, Vents, or premium consumables are worth the trouble.

WHO DOES WHAT

In WoT you have up to five different crew members, each of who has a specific job.

Commander
The commander...commands the vehicle. The commander has two effects on the crew:

• View Range is a progressive stat based on his competency
  
• 1/10 of the commander's skill level is added to the competency of the crew. This is why a 100% crew will actually be at 110% proficiency except for the commander, because they got a 10% bonus.

This makes the commander an incredibly important member of your crew. In the event that he is knocked out, you will notice an overall decrease in the performance of the vehicle.

Driver
The driver drives the vehicle [these names are fairly self explanatory]. The driver's effect on the performance of the vehicle is difficult to quantify, because the numbers aren't exactly given in the game.

• Terrain Resistance is what the driver effects. As he levels up the terrain resistance of the vehicle will decrease, which decreases track friction with the ground.

This means a couple of things. First, you can't actually calculate these values for yourself, because they aren't given in game. However, you can calculate them as a ratio of increased performance you'll get out of them (i.e. 10% better performance at n proficiency). This decrease in terrain resistance also has the added benefit of increasing turn speeds and minimizing the effects of turn bleeding, where turning at high speeds slows down your tank.

Gunner
One of the most important positions in the vehicle, the gunner controls many different aspects of the vehicle at once:

• Accuracy, or the absolute most you can get the aiming reticule to shrink down to.
  
• Aim Time, or how long it takes for that reticule to actually get fully aimed. In some instances, fast aim time is even more important than accuracy.
  
• Aim Bloom. This is one of those stats not listed in the game, but essentially it's how much the aiming reticule will 'bloom' when you move. Higher gunner proficiency will limit the maximum size of the reticule.

These three stats are incredibly important to any vehicle, since they affect your chances to hit something, and how quickly you can do it.

Loader
The loader has but a single job, but it's the one thing that most people will notice the most because it's a stat that is easy to quantify:

• Load Time, how quickly a shell can be loaded.

The loader is very important to tanks at opposite ends of the spectrum: those with incredibly long loading times will need to minimize them, while those that depend on a high rate of fire to be successful need to maximize that statistic.

Radio Operator
The black sheep of the crew, being seen as often quite useless (indeed, many Soviet tanks relegate this role to the commander). His effect is:

• Radio Range, how far your radio can reach other tanks.

This is a rather important skill overall for people who find themselves often fighting further away from support units. Scouts will want to maximize this, so they can relay coordinates to allies, as will TD's and artillery who often find themselves at the rear of a formation.

Overall
Therefore, the following skills are influenced by the crew, and thus will be increased by Brothers in Arms, Vents, and consumables:

• View Range
  
• Radio Range
  
• General Mobility
  
• Aim Time
  
• Accuracy
  
• Reticule Bloom
  
• Reload time

As we can see, that is a lot of stuff that can be affected. Now, for how it's calculated.

HOW IT'S ALL CALCULATED

The formula used to calculate the effectiveness of a crew is rather messed up. It's not complicated per se, but it's a lot of numbers that seemingly make no sense.

Aspects of the vehicle are divided into two types, progressive for stats that get bigger as the skill levels up (reload, view range, etc), and digressive for stats that get smaller (aim time, accuracy, etc).

Progressive stats level as follows:

(D / 0.875)*(0.00375*P+0.5)

Where D is the stat displays and P is the crew's proficiency. A digressive stat levels like this:

(D*0.875)/(0.0375*P+0.5)

Now if you're like me, you probably see that and think "Well ladi-freaking-da...that helps me SOO much". Fortunately, I'm so kind to explain what it means for you...

SIMPLIFIED VERSION

Instead of trying to crunch numbers, here's a handy guide of what happens to crew skills at certain paragon points in their development. Since the rest of the crew gets a commander bonus, I'm going to do a 100% commander first, and then show you what happens when you have a 100% crew with that 100% commander:
Commander Proficiency

• 50%: -21%
  
• 60%: -17%
  
• 70%: -13%
  
• 75%: -11%
  
• 80%: -9%
  
• 90%: -4%
  
• 100%: Displayed Stat

What this means for you is that most displayed stats are working for a crew at 100% proficiency. However, bear in mind that a crew is also influenced by a commander. So, let's say you wish to either retrain a crew or something like that. What is the effect on performance going to be for the rest of the crew?
Crew Proficiency

• 50%: -20%
  
• 60%: -15%
  
• 70%: -10%
  
• 75%: -8%
  
• 80%: -5%
  
• 90%: Essentially the Displayed Stat
  
• 100%: +4% Better

This already begins to highlight the power of a competent commander on your crew. 75% proficiency is what you'd have if you paid for a crew, and they'd be preforming every job 8% worse than what the displayed stats would show. However, this is more than double what a free crew would be able to do.

What About Brother's in Arms, Vents, and Consumables?

The above calculations show what you get from a basic crew, but what if you want more? Here are your options:

• Vents: +5% to crew skills
  
• Brothers in Arms:+5% to crew skills once the entire crew researches it to 100%
  
• Premium Consumables: for a little gold, tack on a whopping 10% more proficiency. Used automatically, and quite costly, so beware.

Here's where this guide becomes important, and the reason I wrote it. A friend of mine was whining about Brother's In Arms (BiA for short), did not work as described. He thought it should take a full 5% off of reload times, when it clearly didn't.

So, this brings up the question of just how effective are vents or BiA? Let's assume you have it on a 100% crew.
With Just Vents or BIA:

• Your commander is going to now have 105% proficiency, so he will give +11% to your crew.
  
• Your crew is going to be at 100%, get a +11% commander bonus, AND a +5% bonus from vents or BiA.
  
• This yields an increase in performance of about 7%

That might seem underwhelming. Without the Vents you're already looking at 4% better performance, so is spending up to 600,000 silver or training your entire crew in a perk worth a 3% increase in performance? Well, bear in mind that the entire crew is getting that bonus, and it will help your vehicle in small ways. Still, this begs the question: what if you got both (or paid gold for consumables?):

With Vents AND BIA:

• Your commander is going to be at 110% proficiency, so your entire crew is going to get a +11% performance boost.
  
• This means your crew is getting 100% proficiency, +11% from the command, +5% from the vents, +5% from the BiA, for a total of 121% proficiency.
  
• This will yield an increased performance of 9%.

9% increase in performance is much, much nicer. Compared to the 4% increase you get without either vents or BIA, the combination of the 2 makes your vehicle 5% better at everything the crew controls, and the combo is 3% better than one or the other individually.

Some may still not like +5% performance though, perfering a larger bonus to everything. However, consider this. A gun rammer will provide +10% to reload time. The combination of vents and BIA only gives +5% reload time. HOWEVER, it's also giving +5% to aim time and +5% to overall accuracy. So the combination of the two is a subtle boost to all your stats, as opposed to a larger one that is localized.

With Everything:

• So you want vents, BIA, AND a premium consumable? Well, your commander will now be at 120% proficiency, conferring a 12% bonus to the crew.
  
• Your crew will be sitting at 100+12+5+5+10, yielding a massive 132% proficiency.
  
• This will give you a performance boost of nearly 14%.

Therefore, if you have the gold your crew will end up doing every job 10% better than they would without any of it. This completely nullifies the need for a gun rammer, gun laying drive, improved grousers, or the standard optics. That is a huge boost, but it will cost you.

IN CONCLUSION

Are vents and Brothers in Arms worth it? Perhaps. Individually the bonus is somewhat small, but together it becomes rather impressive. They will provide an overall bonus that is about half of what the standard equipment will yield. Pairs with the correct equipment you can get some nice bonuses. For example, my KV-2 uses a derp, and it has two stats that annoy me: a 2.5 second round per minute reload, a 6 meter accuracy, and a 4 second aim time. I have vents, a gun rammer, and a gun laying drive. As I level, here are my stats:

• Listed Stats: 2.5 RPM, 6 accuracy, 4 second aim time.
  
• 100% crew: 2.6 RPM, 5.76 Accuracy, 3.84 aim time
  
• With just vents: 2.67 RPM, 5.61 accuracy, 3.74 aim time.
  
• With vents AND BIA: 2.73 RPM, 5.5 accuracy, 3.67 aim time.
  
• 100% with rammer and GLD, but no vents or BiA: 2.86 RPM, 5.76 accuracy, 3.46 aim time.
  
• 100% with everything: 3 RPM, 5.5 accuracy, 3.1 aim time.

This is a not insubstantial increase in performance. I was able to cut the aim time by a full quarter, and the reloads are substantially shorter as well. Where it should take 24 seconds to reload I can get it down to 19.97 seconds (as opposed to just 20.97 seconds with vents and BIA). The combination shaves a full second off the reloads, the aim time is 25% faster, and best of all I can increase the total accuracy. Not to mention I should now have about 5% more view range and radio range, plus a small increase in vehicle driving performance. If i added consumables the performance boost would be even larger.

The combination of BiA and Vents will give you the best performance when you're trying to maximize another stat, but there are situations when you're better off using more specialist skills. A medium tank for example might be better off with smooth ride and snap shot than with BiA. I've found BiA to be most helpful to things like heavy tanks (who are best off trying to maintain a good balance of stats), and artillery because there are very few useful perks and the ability to lower aim time and reloads is incredibly helpful. Medium tanks can benefit from BiA, as can TD's, but I suspect there are more helpful specialist perks and skills for them.

I do have one bit of final advice. If you want Brothers in Arms, make it your first skill. It takes way too long to get a second or third skill leveled up, so you'll be without anything for a long time (this goes for ALL perks). Granted, losing repairs sucks, so here is the solution: level repairs to 100%, and get another miscellaneous skill up to about 40-50%. Then pay to re-spec your entire crew, choosing Brothers in Arms for all of them (it should be at 100%), while repairs is your second one. Since repairs is a skill, you'll get progressively better repair skill as you level, while BiA will always be in effect.
Edited by VRMoran, Jun 07 2012 - 19:57.

wow a lot of words lol

 deadhero454, on Jun 07 2012 - 19:20, said:

lol...sorry about that, but there is a lot to explain and I was trying to avoid sounding "mathy"

lol i know it is good

Bravo!  This is everything I wanted and need to know.  Right now,
I'm trying to get the Duck to go faster.  This helps confirms my
theory and it will be beneficial to me in the future.

This is a well done forum post. Good job, and it actually makes things ALOT clearer. Great job, keep it up lol. Who knows, maybe WG will even make you a forum admin or something lol

<applause>

- applause and +1

Effective Training Level

The training level can be found by hovering the cursor over a crew member in the garage, but note that the display is rounded to the nearest whole number. Also, the consumable bonus is not included because it is only applied once battle starts and the consumable is consumed.
Good post!
here is the info from the WoT Wiki http://wiki.worldoftanks.com/Crew

The effective training level of your crew's skills is not displayed, only the base training level is shown for those. You need to calculate the effective level.

• Maximum effective training level for your Commander is 120% (100% base training level + 5% Brothers in Arms skill + 5% Improved Ventilation equipment + 10% premium consumable bonus).
  
• Maximum effective training level for every other crew member is 132% (120% as above plus 10% Commander bonus).
  
• For tanks that do not have Improved Ventilation Equipment available to them, the maximum training level is 115% for the Commander and 126.5% for his crew.

If several crew members are assigned to the same role, the average of their training level is used to determine your crew's performance in that role. This average is the effective training level. For example, for the two Loaders on an SU-14, if one performs at 50%, and the other at 100%, their average training level of 75% is the effective training level that the SU-14 will operate at.
Non-role-specific skills are averaged across all crew members. Crew members that do not have any training in a certain skill will add a 0% to the averaging calculations. Thus, to reach a 100% effective training level in a non-role specific skill for a tank with a crew of 4, all 4 crew members must reach 100% in that specific skill.
Role-specific skills/perks are not averaged. If multiple crewmen train in the same role-specific skill, only the highest training level will be used.
Edited by husband, Jun 07 2012 - 19:49.

I made sure to include the commander's bonus when calculating BIA and Vents. With just BIA it doesn't yield a bonus (because the commander will be 105%), but with both it will yield another 1% to the crew, raising them to 121% proficiency. These bonuses can be seen when you hover the mouse over the crew member, as you stated.

When I said 50%-60%-75%, etc in the Crew Proficiency part, that was as if you had retrained the crew or something, and has the commander's bonus factored in.

EDIT: I stand corrected. Looking at my T34 Heavy, which has just vents on, the commander is giving him a 11% bonus despite being at 105% proficiency, so I guess it rounds up, not down.
Edited by VRMoran, Jun 07 2012 - 19:53.

By far, the best explanation of crew mechanics I've seen. Bravo +1

Thanks for the guide, this is very helpful to me as I'm getting back into the game after an extended absence.

 VRMoran, on Jun 07 2012 - 19:09, said:

"This completely nullifies the need for a gun rammer, gun laying drive, improved grousers, or the standard optics."  Does this mean that if you have vents, BIA, and a premium consumable you can't improve the aiming and loading times further?  So in this case the rammer and GLD aren't actually helping?  Or do you just mean they're not necessary if you're happy with a 14% improvement?

 twistedspark, on Jun 08 2012 - 05:57, said:

The latter. If you decide to add something like GLD or Rammer you'll end up getting even more performance out of your vehicle.

When using Vents, BiA, and consumables your basically getting the equivelant of improved grousers, a gun rammer, a gun laying driver, binoculars (the regular ones, not the ones that take effect while stationary), plus a bonus to overall accuracy and radio range all at the same time. However, bear in mind that it is going to cost you gold, and the costs add up quickly. If I recall it's 50 gold per consumable.

If you wanted though, you could add, say, a gun rammer on top of all of that and get a tremendous boost to rate of fire (20% faster overall).

I found this very informative, I was actually confused as to why some of my crewmembers have 110% proficiency.

 Steadski, on Jun 15 2012 - 22:33, said:

Good question!

When you look at your crew, the commander is going to give them a bonus eqaul to 10% of his level. So, a 100% crew is actually a 110% crew, because your commander is giving them 10% better proficiency.

This is also why a 100% crew will perform their jobs 4% better than the displayed stats.

In your example when you say 100% with everything does that mean your saying vents+bia+Premium+rammer+gun laying?

If you don't mind since i am bad at math i wanted to figure out my real stats on my kv3 i have vents+bia+rammer+gun kaying device. I am using the d-25t that has a base of 4.88 rpm/.46 accuracy & 3.4 second aim time.

What i came up with was 5.80 rpm/4.19 accuracy and 2.75 second aim time.

Thanks

Awesome post. Just one thing:

Wiki says BIA also adds 5% to Repair, Firefighting and Camo skills along the ones you listed. So this is one more reason why BIA is a great skill to research first on many tanks while leaving the mentoned skills (repair, firefighting, camo) for later, or just use consumables (toolkit, medkit, fire extingusher) or modules (camo net, tooolbox).
Edited by Frijolero, Jun 16 2012 - 20:34.

 darkdog9, on Jun 16 2012 - 18:13, said:

The everything stat is just with BIA, Consumables, and Vents.

The 122mm D-25T has a rate of fire that can range from 3.75 to 4.17rpm depending on what tank it is put on. This represents a 100% proficiency. With vents, BIA, a consumable, AND 100% proficiency, you're rate of fire should be 4.3 and 4.7 rounds per minute. Add a gun rammer to that and it will jump to 4.73 to 5.17 rpm.

Though since yours have a base of 4.88....your math is off a little. With BIA+Vent+Consumable, it should be 5.549 RPM. With just BIA and Vents, it would be 5.32

One thing you can do if you have a graphing calculator is to put these two equations into it:
y1=(DISPLAYED STAT/.875)(.00375*X+.5)
y2=(DISPLAYED STAT*0.875)/(0.0375*P+0.5)

Then, set your window to:

• Xmin=0
  
• Xmax=133
  
• Ymin=0
  
• Ymax=10

Then, when you want to calculate what performance you'll get out of something, take the displayed stat and stick it into the Displayed Stat section for either a digressive or progressive stat (if it gets bigger, it goes into the top one....if it gets smaller, it goes into the second equation), and use the "Trace" function or the Table button to see what different crew proficiencies will do to a stat.

That's how I calculated the values I did.
Edited by VRMoran, Jun 16 2012 - 21:00.

Not sure if this question goes here but....

I have an MS-1.

*waits for laughter to stop*

The problem is that as my crew is going up in their training (currently all at around 92%) they (especially the gunner) seem to be getting worse than they were when they were only 75%. I used to be able to hit tanks with a fair regularity, and even hit tanks that were almost completely hidden behind buildings etc. I'm noticing that hits (especially on partially obscured tanks) are getting fewer and further between. I've tried using auto-aim and not using it. It doesn't seem to make a difference.

Is there something I'm doing wrong? I thought the crew should have been getting better the more training they got, but this does not seem to be the case.

 VRMoran, on Jun 07 2012 - 19:09, said:

You somehow write a wall of text and completely ignore what your friend said.  He said it wasn't giving him a 5% boost in performance.  You then turn around and claim it will give a 7% boost.  He is correct.  You are wrong.  BIA or Vents by themselves will boost performance in most areas by 2.2%, not 5% and certainly not 7%.  Actually, what you are looking at is the combined effect of EVERYTHING being used to boost performance - not just BIA.

If you use your own numbers you can confirm BIA provides a boost under 3%.  The average is about 2.2% boost in performance.

While it is true that 2.2% boost is applied to all crew positions, it is also true every crew position has skills/perks which provide greater benefits individually. For this reason, on most tanks, BIA should not be taken til the 3rd or 4th skill/perk.
Edited by Tazilon, Oct 03 2012 - 15:55.