Metrigy counted 117.1 million UCaaS seats worldwide at the end of 2025, up 6.9% in a year, and the four biggest vendors (Microsoft, Cisco, Zoom and RingCentral) now hold 53% of them. Yet cloud telephony is far from finished: Cavell estimates that 392 million of 467 million addressable business users (82%) still have not moved to a cloud communications service. The market is also growing slowly in dollars, at 6.1% to $23.0 billion in 2025, because most of the easy PBX migrations are done and providers now win customers from each other. For the voice-over-IP side of the same shift, see our VoIP and UCaaS statistics. We aggregated data from Metrigy, Cavell, Synergy Research Group, Microsoft, Zoom, RingCentral and 8x8 SEC filings and earnings calls, Mordor Intelligence, Future Market Insights and other primary sources listed in the methodology.
TL;DR
- 117.1 million UCaaS seats worldwide in 2025, up 6.9% from 2024 (Metrigy UCaaS Quarterly Market Share and Forecast Report, April 2026).
- Microsoft leads 2025 UCaaS seats at 22.2%, ahead of Cisco 16.5%, Zoom 8.3% and RingCentral 6.4% (Metrigy, 2026).
- The Big 4 vendors make up 53% of the total UCaaS market (Metrigy press release, March 2026).
- Global UCaaS revenue reached $23.0 billion in 2025, up 6.1%, with $28.0 billion forecast for 2030 (Metrigy, 2026).
- 392 million of 467 million addressable users (82%) have not yet moved to cloud communications (Cavell, June 2025).
- Microsoft Teams Phone passed 26 million PSTN users at the end of 2025, up about 30% from 20 million in April 2024 (Microsoft via Dstny and UC Today).
- Zoom Phone surpassed 10 million paid seats in late 2025 (Zoom Q3 FY2026 earnings call).
- On-premises PBX and UC revenue fell 6% to $1.8 billion in 2025 and IP desk phones are forecast to drop 17.6% in 2026 (Metrigy, March 2026).
- RingCentral ARR reached $2.76 billion at June 30, 2026, up from $2.59 billion (RingCentral Form 10-Q, Q2 2026).
- 13% of RingCentral ARR comes from customers using a paid native AI product, double a year earlier (RingCentral Q2 2026 results).
- 41.4% of businesses have no plans to replace their primary UCaaS provider (Metrigy, 2026).
- 49% of cloud communications providers now win most customers from competitors rather than on-premises migrations (Cavell 2024 Cloud Comms Market Reports).
1. The Global Seat Base: 117 Million Seats, Most of the Market Still Ahead
The seat count is now large, but its growth rate shows a maturing market. Metrigy’s UCaaS Quarterly Market Share and Forecast Report puts worldwide UCaaS seats at 117.1 million in 2025, up 6.9% over 2024, after 114.0 million at mid-year. That is single-digit growth on a base that Synergy Research Group measured at under 8 million subscribers in 2018. Metrigy’s own analyst summary is that with ‘over half of users now on a UCaaS platform, overall revenue growth for the market has slowed.’
The other half is the opportunity every vendor is chasing. Cavell’s June 2025 analysis estimates a global available market of 467 million users, with 392 million (82%) not yet on a cloud communications solution and penetration just over 18%. Zoom framed the same headroom on its Q2 FY2027 call: roughly 130 million cloud seats and 150 million equivalent on-premises seats available to win. The two views differ mainly in what counts as an addressable seat (see the Data watch note), but both agree the installed base of legacy phones is still large.
| Metric | Value | Source |
|---|---|---|
| Worldwide UCaaS seats, 2025 | 117.1 million (+6.9% vs 2024) | Metrigy UCaaS Quarterly Market Share and Forecast Report, April 2026 |
| Worldwide UCaaS seats, 1H2025 | 114.0 million (+4.0% vs year-end 2024) | Metrigy UCaaS Size and Spending Forecast, 1H25 Update |
| Telephony seats still on customer-owned or dedicated hosted platforms | Nearly 50% | Metrigy, 1H25 Update |
| Global available market for cloud comms | 467 million users | Cavell, June 2025 |
| Users not yet migrated to cloud comms | 392 million (82%); penetration just over 18% | Cavell, June 2025 |
| US UCaaS installed base | Over 39 million users (largest globally) | Cavell, June 2025 |
| Seats Zoom calls available to win | About 130 million cloud + 150 million on-premises equivalent | Zoom Q2 FY2027 earnings call, August 2026 |
| UCaaS users forecast for end of 2028 | More than 131 million (10.3% CAGR) | Cavell 2024 Cloud Comms Market Reports |
Historical context (most recent available public data: Synergy Research Group, 2018 to 2022): Synergy counted a UCaaS subscriber base approaching 8 million in Q2 2018, approaching 14 million in Q3 2020, more than 17 million in Q1 2021 and more than 21 million in Q2 2022, with the US accounting for about 75% of subscribers (Synergy Research Group, September 2022). Synergy’s narrower subscriber definition explains most of the gap with Metrigy’s 117 million seats.
2. Vendor Market Share: Microsoft Leads, the Big Four Hold 53%
Seat share has shifted toward the collaboration suites. Microsoft held 22.2% of UCaaS seats in 2025, followed by Cisco at 16.5%, Zoom at 8.3% and RingCentral at 6.4% (Metrigy, 2026), and Metrigy’s March 2026 press release says these four make up 53% of the total market. Five years earlier the ranking was different: in Q1 2021 Synergy ranked RingCentral first by revenue and noted that Microsoft was ‘doubling its UCaaS subscriber base every six months’ (Synergy Research Group, June 2021).
Microsoft’s lead comes from attaching voice to an existing Teams base, and that attach rate is still low. Microsoft said Teams Phone passed 26 million PSTN-enabled users at the end of 2025, about 30% more than the 20 million reported in April 2024 (Dstny; UC Today). Against 320 million Teams monthly active users (Microsoft FY24 Q1 earnings, October 2023), Cavell’s Patrick Watson puts voice penetration at only about 6%. Zoom Phone crossed 10 million paid seats in late 2025. For meeting-side usage of the same platforms, see our video conferencing statistics.
| Metric | Value | Source |
|---|---|---|
| UCaaS seat share, 2025 | Microsoft 22.2%, Cisco 16.5%, Zoom 8.3%, RingCentral 6.4% | Metrigy UCaaS Quarterly Market Share and Forecast Report, April 2026 |
| UCaaS seat share, 1H2025 | Microsoft 21.7%, Cisco 15.1%, Zoom 8.8%, RingCentral 6.4% | Metrigy, 1H25 Update |
| Big 4 combined share of UCaaS market | 53% | Metrigy press release, March 19, 2026 |
| Microsoft Teams Phone PSTN users | 26 million (end of 2025), from 20 million (April 2024) | Microsoft via Dstny, January 2026 |
| Microsoft Teams monthly active users | 320 million | Microsoft FY24 Q1 earnings, October 2023 |
| Teams user base that is voice-enabled | About 6% | Cavell (Patrick Watson) via UC Today |
| Zoom Phone paid seats | More than 10 million (early fiscal Q3 2026) | Zoom Q3 FY2026 earnings call, November 2025 |
| On-premises PBX and UC revenue leader, 2025 | Cisco, 45.8% | Metrigy press release, March 2026 |
Context note: the Teams MAU figure dates from 2023 (most recent figure Microsoft has stated on an earnings call that we could verify), while Cavell’s 6% estimate refers to a base of ‘350 million-plus’ Teams users. Seat share counts licenses, not revenue, so low-priced bundled seats weigh as much as premium ones.
3. Market Revenue: Cloud Grows Slowly, Legacy Hardware Collapses
Revenue tells a quieter story than seats. Metrigy sized the UCaaS market at $23.0 billion in 2025, up 6.1%, after $21.7 billion (+6.5%) in 2024, and expects just 6% growth in 2026 and a 4.0% CAGR to $28.0 billion by 2030. Per-seat prices are under pressure because bundles (Teams, Zoom Workplace) compete with standalone cloud PBX, so seats grow slightly faster than dollars.
The legacy side is shrinking faster than the cloud side is growing. IP desk phone revenue is forecast to fall 17.6% in 2026, after a 4% decline to $782.9 million in 2025, and on-premises PBX and UC revenue fell 6% to $1.8 billion with an 8.7% decline expected in 2026 (Metrigy, March 2026). SIP trunking, the bridge that lets Teams and other platforms reach the phone network, is the healthy exception at $13.5 billion and +8.7%.
| Metric | Value | Source |
|---|---|---|
| Global UCaaS market, 2025 | $23.0 billion (+6.1%) | Metrigy press release, March 2026 |
| Global UCaaS market, 2024 | $21.7 billion (+6.5%) | Metrigy UCaaS Size and Spending Forecast, 1H25 Update |
| UCaaS market forecast, 2030 | $28.0 billion (4.0% CAGR 2025 to 2030) | Metrigy, April 2026 |
| On-premises PBX and UC revenue, 2025 | $1.8 billion (-6%); -8.7% forecast for 2026 | Metrigy, March 2026 |
| IP desk phone revenue, 2025 | $782.9 million (-4%); -17.6% forecast for 2026 | Metrigy, March 2026 |
| SIP trunking revenue, 2025 | $13.5 billion (+8.7%); +8% forecast for 2026 | Metrigy, March 2026 |
| Enterprise SBC revenue, 2025 | $437.1 million (-7%); Oracle leads with 19.9% | Metrigy, March 2026 |
Cross-check: other research firms define UCaaS far more broadly (adding collaboration software, video and messaging) and report much larger numbers. Mordor Intelligence values the market at $70.56 billion in 2026 with a 25.67% CAGR to 2031, and Future Market Insights at $37.17 billion in 2026 with a 13.2% CAGR to 2036. We use Metrigy as the anchor because it publishes seat counts and vendor shares under the same definition.
4. Vendor Results: Single-Digit Growth at the Cloud Specialists
The public UCaaS specialists confirm that the land-grab phase is over. RingCentral’s ARR reached $2.76 billion at June 30, 2026, up from $2.59 billion a year earlier (RingCentral Form 10-Q, Q2 2026), with total revenue up 5.9% to $657 million and net monthly subscription dollar retention above 99%. Zoom’s Q2 FY2027 results show the same split: Enterprise revenue grew 7.8%, its fastest in three years, while Online (small business and consumer) revenue grew 0.6%.
The pattern is consistent: growth now comes from selling more products to existing large accounts, not from new seats in small offices. Zoom Phone is still growing in the teens year over year, and 8x8’s Q1 FY2027 results show service revenue up 5% with platform usage revenue up about 63% to 26% of service revenue, meaning metered usage (messaging, voice APIs, AI) is outgrowing per-seat licenses. Churn dynamics behind these numbers are covered in our SaaS churn statistics.
| Metric | Value | Source |
|---|---|---|
| RingCentral ARR, June 30, 2026 | $2.76 billion (vs $2.59 billion a year earlier) | RingCentral Form 10-Q, Q2 2026 |
| RingCentral Q2 2026 revenue / subscriptions revenue | $657 million (+5.9%) / $634 million (+5.8%) | RingCentral Q2 2026 results, July 23, 2026 |
| RingCentral FY2026 revenue guidance | $2.635 to $2.646 billion | RingCentral Q2 2026 results |
| Zoom Q2 FY2027 total / Enterprise revenue | $1,277.2 million (+4.9%) / $787.5 million (+7.8%) | Zoom Q2 FY2027 results (SEC Exhibit 99.1), August 2026 |
| Zoom customers over $100K trailing revenue | 4,625 (+8.2%); Enterprise net dollar expansion 99% | Zoom Q2 FY2027 results |
| Zoom Online average monthly churn | 2.9% (flat year over year) | Zoom Q2 FY2027 results |
| 8x8 Q1 FY2027 service revenue | $185.3 million (+5%) | 8x8 Q1 FY2027 results (SEC Exhibit 99.1), August 4, 2026 |
| 8x8 platform usage revenue | About 26% of service revenue (+63% YoY) | 8x8 Q1 FY2027 earnings call |
Context note: these are company-wide figures that include contact center, video and AI products, not pure UCaaS seat revenue. None of the three companies discloses total seat counts on a quarterly basis.
5. AI Is the New Seat Driver
With seat growth in single digits, vendors now sell AI on top of the phone line, and the uptake is fast. 13% of RingCentral’s ARR now comes from customers using at least one native paid AI product, double the share a year earlier, and the company ended Q2 2026 with more than 16,000 paying AI Receptionist customers, up 400% (RingCentral Q2 2026 results; earnings call transcript). AI receptionists matter because they answer the calls that a human-staffed phone seat used to cover, a shift we track in our voice agent and contact center automation statistics.
Zoom reports the same direction: licensed monthly active users of AI features in Workplace grew 125% year over year, Zoom Virtual Agent customers grew 256%, and paid AI was in 9 of its top 10 customer experience deals (Zoom Q2 FY2027 earnings call). At 8x8, AI solution adoption rose 121%. On the buyer side, Metrigy lists lack of AI features as the second most common reason businesses switch UCaaS providers, behind cost.
| Metric | Value | Source |
|---|---|---|
| RingCentral ARR from customers using paid AI | About 13% (doubled YoY) | RingCentral Q2 2026 results |
| RingCentral AI Receptionist paying customers | More than 16,000 (+400% YoY) | RingCentral Q2 2026 earnings call |
| RingCentral AI Conversation Expert customers | More than 6,300 (+70% YoY) | RingCentral Q2 2026 earnings call |
| RingCentral AI-led new product ARR growth, 1H 2026 | Nearly 60% | RingCentral Q2 2026 earnings call |
| Zoom licensed MAU of Workplace AI features | +125% YoY | Zoom Q2 FY2027 earnings call |
| Zoom Virtual Agent customer count | +256% YoY; paid AI in 9 of top 10 CX deals | Zoom Q2 FY2027 earnings call |
| 8x8 AI solution adoption | +121% YoY; over 200 organizations building agents | 8x8 Q1 FY2027 earnings call |
| Microsoft 365 Copilot paid seats | Over 30 million | Microsoft FY26 Q4 earnings, July 29, 2026 |
Context note: vendor AI metrics use different bases (ARR share, customer counts, MAU growth) and are not comparable across companies. Microsoft’s Copilot seats cover all of Microsoft 365, not only Teams Phone.
6. Buyer Behavior and Provider Economics
The buyers who are left are harder to win, and many are already on the cloud. Metrigy’s 2025 survey data shows 58.6% of businesses use only UCaaS, while 32.7% run multiple phone system types, and 41.4% plan to stay with their primary provider. The remaining switchers move for cost, AI features and integrations, in that order.
That turns UCaaS into a replacement market. Cavell’s 2024 Cloud Comms Market Reports, based on more than 100 service providers in the UK, Europe and the US, found 49% of providers now win most of their customers from competitors, the first time this matched wins from on-premises migrations, and more than 40% reported falling UCaaS revenue. Zoom says all 10 of its top 10 Phone deals in Q2 FY2027 were takeouts. Hybrid and remote work patterns, covered in our remote work statistics, keep mobile and softphone seats in demand.
| Metric | Value | Source |
|---|---|---|
| Businesses using only UCaaS | 58.6% | Metrigy UCaaS Quarterly Market Share and Forecast Report, April 2026 |
| Businesses running multiple phone system types | 32.7% | Metrigy, April 2026 |
| Businesses with no plans to replace primary provider | 41.4% | Metrigy, April 2026 |
| Businesses using same vendor for contact center and UC | 31.6% | Metrigy, April 2026 |
| Providers winning most customers from competitors | 49% | Cavell 2024 Cloud Comms Market Reports |
| Providers reporting decreased UCaaS revenue / diversifying portfolios / adding AI | 40%+ / 62% / 48% | Cavell 2024 Cloud Comms Market Reports |
| Mobile UCaaS share of the market | Over 15% | Cavell 2024 Cloud Comms Market Reports |
| 8x8 customers using 3+ paid products | +18% YoY, about 38% of recurring revenue | 8x8 Q1 FY2027 earnings call |
Context note: Cavell’s provider survey dates from early 2024 (most recent available public summary); its 2026 market reports are sold privately.
Summary: UCaaS Seat Adoption by the Numbers
| Metric | Value | Source |
|---|---|---|
| Worldwide UCaaS seats, 2025 | 117.1 million (+6.9%) | Metrigy, April 2026 |
| Worldwide UCaaS seats, 1H2025 | 114.0 million | Metrigy, 1H25 Update |
| Users not yet on cloud comms | 392 million of 467 million (82%) | Cavell, June 2025 |
| US UCaaS installed base | Over 39 million users | Cavell, June 2025 |
| UCaaS users forecast, 2028 | More than 131 million | Cavell, 2024 |
| Microsoft UCaaS seat share | 22.2% (2025) | Metrigy |
| Big 4 vendor share | 53% | Metrigy, March 2026 |
| Microsoft Teams Phone PSTN users | 26 million (end of 2025) | Microsoft via Dstny |
| Teams voice penetration | About 6% | Cavell via UC Today |
| Zoom Phone paid seats | More than 10 million | Zoom, Q3 FY2026 |
| Global UCaaS market, 2025 | $23.0 billion (+6.1%) | Metrigy |
| UCaaS market, 2030 forecast | $28.0 billion (4.0% CAGR) | Metrigy |
| IP desk phone revenue, 2026 forecast | -17.6% | Metrigy |
| On-premises PBX and UC revenue, 2025 | $1.8 billion (-6%) | Metrigy |
| RingCentral ARR | $2.76 billion (June 30, 2026) | RingCentral Form 10-Q |
| RingCentral ARR from paid AI users | About 13% (doubled) | RingCentral Q2 2026 |
| Zoom Enterprise revenue growth | +7.8% (Q2 FY2027) | Zoom |
| Zoom Workplace AI licensed MAU | +125% YoY | Zoom Q2 FY2027 call |
| Businesses using only UCaaS | 58.6% | Metrigy |
| Providers winning most customers from rivals | 49% | Cavell, 2024 |
Methodology and Sources
Every figure above was read during research for this article and traced to the organization that produced it. Where only an earnings call contained a number, we cite the published transcript. Vendor-blog summaries and SEO listicles (including a widely repeated ‘120 million UCaaS seats’ figure attributed to Synergy without a primary document) were excluded.
- Metrigy: Global UCaaS market press release, March 19, 2026, UCaaS Quarterly Market Share and Forecast Report: 2025 and 4Q25, UCaaS Size and Spending Forecast: 1H25 Update
- Cavell: Is there any space left in the UCaaS market? (June 2025); 2024 Cloud Comms Market Reports via Telecoms Tech News and UC Today
- Synergy Research Group: Q2 2022 UCaaS subscribers, Q1 2021, Q3 2020, Q2 2018
- Microsoft: FY24 Q1 earnings (Teams 320 million MAU), FY26 Q4 earnings (Copilot seats); Teams Phone 26 million via Dstny and UC Today
- Zoom: Q2 FY2027 results, SEC Exhibit 99.1, Q2 FY2027 call transcript, Q3 FY2026 call transcript (10 million Phone seats)
- RingCentral: Q2 2026 Form 10-Q, Q2 2026 results press release, Q2 2026 call transcript
- 8x8: Q1 FY2027 results (SEC Exhibit 99.1); call metrics via Yahoo Finance earnings call highlights
- Market sizing cross-checks: Mordor Intelligence UCaaS Market Report, Future Market Insights UCaaS Market
- Data watch: Seat counts depend heavily on definitions. Metrigy reports 117.1 million UCaaS seats for 2025, Synergy’s last public subscriber count was just over 21 million in Q2 2022 (a narrower, mostly cloud PBX scope), and Cavell’s 2024 forecast of 131 million users by 2028 sits close to Metrigy’s current figure. Cavell’s June 2025 article cites ‘over 12 million’ Teams voice-enabled users while Microsoft reported 26 million Teams Phone PSTN users at the end of 2025; the Cavell figure appears to reflect an older data point or a narrower definition, so we cite Microsoft’s number for Teams Phone. Market revenue conflicts sharply: Metrigy ($23.0 billion, 2025), Future Market Insights ($37.17 billion, 2026) and Mordor Intelligence ($70.56 billion, 2026) use different scopes; Future Market Insights also lists vendor share ranges (for example RingCentral 12 to 18%) that differ from Metrigy’s seat shares, which we do not use. Gartner, IDC and Frost and Sullivan UCaaS data is paywalled and was not used. Synergy figures from 2018 to 2022 and Microsoft’s 2023 Teams MAU are most recent available public data. Vendor AI and revenue metrics are company-reported and unaudited outside the SEC filings.
Last updated: October 3, 2026. We update this roundup quarterly, and the next refresh is expected when Metrigy publishes its 1H26 UCaaS market share update and RingCentral, Zoom and 8x8 report their next quarterly results in November 2026.