What is the forecasted range of 5G devices for 2021 
ment and the inventory environment that you're in heading into the strongest part of the year?
Akash Palkhiwala -- Executive Vice President and Chief Financial Officer
Yes. Hi. This is Akash. So we're seeing some minor elevated demand across certain OEMs, given the uncertainty of the OEM mix, especially in China and how things play out, so that's already contemplated in our forecast.
As we look forward â and in our forward commentary as well. As we look forward, we expect some uncertainty over the next few months. But really, when you step back from that and just look at overall design win pipeline and customer traction, it's really very consistent with the comment Cristiano made earlier, where our technologies and our portfolio are really set up to take benefit from it, whether it's Huawei, if we're allowed to ship to them or if other OEMs pick up that share.
Joe Moore -- Morgan Stanley -- Analyst
OK. Great. Thank you. And then are you guys constrained at all on foundry capacity? Are there any supply constraints that we should be aware of?
Cristiano Amon -- President
Joe, this is Cristiano. We're very diversified from a supply standpoint. I think we're probably one of the few companies that have leading now the supply diversity. We are all seeing demand upside.
We're driving a lot of our supply. And I will say that probably, you're going to see some tightness of supply as we have this peak of demand, but we feel good about how we look about the year in 2021.
Joe Moore -- Morgan Stanley -- Analyst
Thank you.
Operator
Next question comes from the line of Blayne Curtis with Barclays. Please proceed with your question.
Blayne Curtis -- Barclays -- Analyst
I just want to follow-up on Joe's question. Just kind of curious, as you look at the builds you're seeing today and then kind of the visibility on models. I think people have looked at some of the stats from the China market saying it's already 60% 5G. Kind of just curious, with these builds, the strong builds you're seeing now, if you had any perspective where we're at in that adoption curve of 5G already? And then kind of just trying to parse it together, you're not getting MSM guidance anymore, but I mean, are we already pretty close to that kind of run rate for 5G on a quarterly basis?
Cristiano Amon -- President
Blayne, this is Cristiano. When you think about China market, we're very happy because the price points of 5G became very aggressive, and we saw that even starting in the last quarter, and that's driving probably more than 50% of all the new activations and all of the new phone launches with 5G. We like that position. As Akash outlined in the prior question, we're very well hedged regardless of who wins in the marketplace.
And we expect the China-accelerated transition of 5G with lower price points to have an impact in how we're going to see this unfolding in emerging markets as China provide a lot of the handsets for emerging markets as well.
Akash Palkhiwala -- Executive Vice President and Chief Financial Officer
And then also just to add, that we are providing an additional data point on the 5G side on the total size of the market for 2021. We are forecasting a range of 450 million to 550 million devices, which really, when you look at a year-over-year basis, that's 150% growth. So extremely strong growth going into it. And as we exit the calendar year 2020, we're seeing that velocity going into '21.
Blayne Curtis -- Barclays -- Analyst
And then a follow-up. Just really appreciate the segment detail. When you look at IoT, you answered why it's spiking up so much. I'd be curious to know a little bit more about the history of that segment.
It looks like you kind of model it back to the details you gave, it's been running around $700 million a quarter. So I'm just trying to put in perspective the strength you're seeing here, and how to think about it going forward. Obviously, everybody is seeing a big work-from-home push. But as you move forward, does some of that roll off? Or has this business been at higher levels prior? Just any context would be great.
Ak
ment and the inventory environment that you're in heading into the strongest part of the year?
Akash Palkhiwala -- Executive Vice President and Chief Financial Officer
Yes. Hi. This is Akash. So we're seeing some minor elevated demand across certain OEMs, given the uncertainty of the OEM mix, especially in China and how things play out, so that's already contemplated in our forecast.
As we look forward â and in our forward commentary as well. As we look forward, we expect some uncertainty over the next few months. But really, when you step back from that and just look at overall design win pipeline and customer traction, it's really very consistent with the comment Cristiano made earlier, where our technologies and our portfolio are really set up to take benefit from it, whether it's Huawei, if we're allowed to ship to them or if other OEMs pick up that share.
Joe Moore -- Morgan Stanley -- Analyst
OK. Great. Thank you. And then are you guys constrained at all on foundry capacity? Are there any supply constraints that we should be aware of?
Cristiano Amon -- President
Joe, this is Cristiano. We're very diversified from a supply standpoint. I think we're probably one of the few companies that have leading now the supply diversity. We are all seeing demand upside.
We're driving a lot of our supply. And I will say that probably, you're going to see some tightness of supply as we have this peak of demand, but we feel good about how we look about the year in 2021.
Joe Moore -- Morgan Stanley -- Analyst
Thank you.
Operator
Next question comes from the line of Blayne Curtis with Barclays. Please proceed with your question.
Blayne Curtis -- Barclays -- Analyst
I just want to follow-up on Joe's question. Just kind of curious, as you look at the builds you're seeing today and then kind of the visibility on models. I think people have looked at some of the stats from the China market saying it's already 60% 5G. Kind of just curious, with these builds, the strong builds you're seeing now, if you had any perspective where we're at in that adoption curve of 5G already? And then kind of just trying to parse it together, you're not getting MSM guidance anymore, but I mean, are we already pretty close to that kind of run rate for 5G on a quarterly basis?
Cristiano Amon -- President
 Blayne, this is Cristiano. When you think about China market, we're very happy because the price points of 5G became very aggressive, and we saw that even starting in the last quarter, and that's driving probably more than 50% of all the new activations and all of the new phone launches with 5G. We like that position. As Akash outlined in the prior question, we're very well hedged regardless of who wins in the marketplace.
And we expect the China-accelerated transition of 5G with lower price points to have an impact in how we're going to see this unfolding in emerging markets as China provide a lot of the handsets for emerging markets as well.
Akash Palkhiwala -- Executive Vice President and Chief Financial Officer
And then also just to add, that we are providing an additional data point on the 5G side on the total size of the market for 2021. We are forecasting a range of 450 million to 550 million devices, which really, when you look at a year-over-year basis, that's 150% growth. So extremely strong growth going into it. And as we exit the calendar year 2020, we're seeing that velocity going into '21.
Blayne Curtis -- Barclays -- Analyst
And then a follow-up. Just really appreciate the segment detail. When you look at IoT, you answered why it's spiking up so much. I'd be curious to know a little bit more about the history of that segment.
It looks like you kind of model it back to the details you gave, it's been running around $700 million a quarter. So I'm just trying to put in perspective the strength you're seeing here, and how to think about it going forward. Obviously, everybody is seeing a big work-from-home push. But as you move forward, does some of that roll off? Or has this business been at higher levels prior? Just any context would be great.
Ak