Tim Cook, chief executive officer of Apple Inc., smiles while speaking about Apple TV+ during an event at the Steve Jobs Theater in Cupertino, California, U.S., on Tuesday, Sept. 10, 2019.

Apple's forthcoming streaming service could rack up over 100 million subscribers in a year, Barclays analysts estimated in a note on Thursday.

Apple TV+ launches on Nov. 1 for $4.99 per month, offering original shows bankrolled by Apple. It'll also be free for a year if you buy a new Apple gadget.

It's entering a competitive market: Disney is also preparing a streaming service launch on November 12, NBC plans a service next year and AT&T's WarnerMedia will also launch a competing product under the HBO brand name. Netflix is the current leader in the market with over 158 million subscribers.

But the free year of Apple TV+ with the purchase of new hardware will help Apple build up a massive subscriber base in a short period of time, Barclays analyst Tim Long said in the note.

Here's how Barclays got to that number, from Thursday's note:

"We model 222M hardware devices sold by Apple over the next 12 months."

"We assume that about 50% of those buying a device in the first year will accept the service, yielding well over 100M subscribers a year from now. We exclude sales to China and our estimate of second and third devices at families."

"We assume that the trial period will last for one year, at which point we expect subscribers to decline as users opt out, and are partially offset by new additions. Of course the rate of churn will depend meaningfully on how quickly Apple can ramp up its content library."

Long says in the note that he sees Apple TV+ being the key growth driver for the stock over the next year, and that he believes the way that Apple will account for the free trial will move sales from the hardware line items on the balance sheet to services revenue.

"From an accounting perspective, for each user that is assumed to take the service, Apple will record a $60 contra revenue item to the hardware, and commence recognizing $4.99 per month in Service revenue," according to the note.

In September, Goldman Sachs analysts made a similar prediction about Apple TV+ accounting.

Apple disagreed.

"We do not expect the introduction of Apple TV+, including the accounting treatment for the service, to have a material impact on our financial results," Apple told CNBC in a statement at the time.

Barclays raised Apple's price target to $224 per share from $207 per share.