PS Plus subscriptions could be less than 10 million. Yay math!
PlayStation Plus is undoubtedly one of the greater services offered by a gaming company. Free games, tons of discounts, and exclusive invites into betas and demos are just a few perks of signing up for Sony's service which is totally optional for PlayStation owners (though now required to play games online with the PS4). But how many people are actually paying for it?
In the most recent earnings call to investors, Sony revealed that PlayStation Network has about 150 million accounts, a number that is growing since the launch of the PS4; but, when it comes to numbers regarding its PlayStation Plus service Sony is a bit more tightlipped, refusing to reveal exact numbers. It makes it hard for us to gage the success of PS Plus, despite Sony's CFO Masaru Kato calling it "very promising" for the company.
However, using some info previously mentioned in past conferences and briefings along with Sony CEO Kazuo Hirai's tackedon comments in the latest earnings call, I believe I've got a fairly accurate estimate for how many PS Plus subscribers there are: and it's less than 10 million.
So how did I arrive at this number?
First we need to go back to January when Sony announced that cumulative PS4 sales surpassed 4.2 million units. In that press release, Sony also mentioned that "Global PS Plus subscriptions have increased by more than 90% since the PS4 launch."
Okay, so that's great and all, but to know the new number we need to first know how many subscribers there were before the PS4s launch. And, again, with Sony not ever mentioning specifics that's hard to do.
Except for the fact that Kazuo Hirai dropped a golden nugget during the earnings call, adding "a little more color" to Kato's initial PS Plus comments. Hirai revealed that of the 4.2 million PS4 owners, more than half have signed up for the PS Plus service. Bingo.
For the same of simplicity let's just say exactly half of all PS4 owners are PS Plus subscribers, so 2.1 million. That 2.1 million is a 90% increase over what the previous number of PS Plus subscribers was. These are new subscribers in addition to the previous number since they come from the PS4s launch (note: this isn't taking into account the number of PS3 owners upgrading to PS4 who are carrying over the PS Plus membership).
Okay, so we now know that 2.1 million is a 90% increase over the previous number. Let's do some math. First we need to figure out what that previous number is (whatever it was, 2.1 million is 90% more).
Running some rough calculations, I found that previous number to be about 2,350,000. I double check the math using a percentage formula:
Using the formula below, new value (2,350,00 + 2,100,000 = 4,450,000)  old value (2,350,000) divided by old value (2,350,000) multiplied by 100% should give us a 90% increase. This would assure us that our estimate of the old value is correct.
New Value  Old Value

× 100% 
___________________  
Old Value

4,450,000  2,350,000

× 100% 
_________________  
2,350,000

We get that 2.1 million would be a 89.36% of 2.35 million which is close enough for our estimate. So we know our math is right.
So what does all of this mean?
Assuming exactly 2.1 million PS4 owners are PS Plus subscribers, then the total number of PS Plus subscribers right now is just 4,450,000.
Keep in mind this is a very conservative number. Let's get a little more generous and assume a whopping 4 million PS4 owners are PS Plus subscribers. Using the same calculations, that would put the previous number of subscribers at around 4,450,000, and the total new value at  the most  8,450,000 PS Plus subscribers. The math checks out below:
New Value  Old Value  × 100% 
___________________  
Old Value 
8,450,000  4,450,000  × 100% 
__________________  
4,450,000 
We get that 4 million would be a 89.88% of 4.45 million which, again, is accurate enough for our estimate.
Okay, so what did we learn here? Aside from math being very confusing, the best possible PS Plus scenario  given what Sony has chosen to reveal  is an at best total of 8.45 million current PlayStation Plus subscribers. It's not a great number considering over 80 million PS3s have been sold, but it's important to remember that prior to it being mandatory to play PS4 games online, PS Plus was merely a perk. I assume this number will grow as more PlayStation 4 consoles are sold.
Make sense? Again, feel free to double check my math. We're writers at GameZone, not mathematicians.