Google is now activating 160,000 mobile phones using its Android software a day, equivalent to 4.8m a month, according to the company's chief executive, Eric Schmidt.

The number is also accelerating, having been put at 100,000 a day in the third week of May during Google's annual I/O conference, Schmidt said – indicating sales growth of 60% per month.

"We have seen a tremendous increase in adoption," Schmidt said in an interview exclusive to the Guardian in the UK. "We've also seen a growth in the number of apps available for Android – there are now approximately 65,000 compared to only 50,000 a month ago." He believes that that means Android could have reached the volume necessary to become an essential mobile operating system – and perhaps the equivalent of Windows on PCs.

At those numbers, roughly 15m Android smartphones would be sold every quarter, compared with a worldwide total of 54m sold in the first quarter of 2010, according to the research company Gartner.

Though Schmidt's announcement was clearly timed to steal some of the thunder of Apple's launch in five countries of the iPhone 4 on Thursday, Schmidt declined to compare the Android platform's market position against its better-known rival. Apple has said that it had orders of 600,000 in a single day for the iPhone 4 last week, and was unable to keep up with demand.

Google is notified whenever a smartphone using the Android operating system is activated by a mobile network. In the US, a number of different models are sold on different networks from different manufacturers, including Motorola, which on Wednesday unveiled its latest Droid X phone on the Verizon network. "It's the best phone ever made on the fastest network," Schmidt said – which could be seen as a dig at AT&T, which has the exclusive contract to sell the iPhone in the US but has struggled to satisfy users' demands for mobile data bandwidth.

Asked whether he saw Apple or Nokia – which has the largest market share of smartphones – as Android's biggest competitor, Schmidt said: "I try to spend my time not focusing on those questions."

Android is a free mobile operating system which any handset maker can use and alter to produce a new version, while developers are able to write apps which will work on any specific version of the system.

However, while Apple has maintained a tight focus on its App Store, which has roughly 250,000 free and paid-for apps available, Google offers them via a "Marketplace", and allows any app to run on Android "as long as it does not harm the network," Schmidt said.

But calculations by a company called Larva Labs, which develops for Android, suggest that iPhone developers may be faring better financially than those on the Android Marketplace. Steve Jobs said earlier this month that Apple has paid out $1bn to developers through a revenue split (which has earned Apple roughly $420m).

By contrast, Larva Labs reckons that Android developers have only earned $20m in total from the Marketplace. Schmidt said he had not seen the figures, but added: "Developers go where the volume is. That's the most important lesson of platform economics: it's all about scale and volume. It's very important that developers get to a scale where they can see the ability to get to a very large audience. We believe we have done so."

Asked whether Android could become the equivalent of Windows for PCs – the dominant operating system – Schmidt said: "The advantage with Android is that anybody can use it. In many ways it is better than Windows because it's free, rather than Windows which had an ever-increasing price point."

He declined to say whether Google has been talking to Nokia about the possibility of an Android-driven Nokia phone, or whether Google would release its own tablet computer similar to Apple's iPad, which has sold 3m units in 90 days.