Quanterix Corporation
Quanterix Corporation (QTRX) Stock Ownership
Institutional vs insider vs public ownership from 13F and float data — top holders, activity, and insider trades below.
SEC 13F · FMP · QTRX · as of Sep 30, 2025
Ownership Breakdown
130
Institutional Holders
▼ 7 vs Q2
$193.73M
Total Inst. Value
▼ $37.61M vs Q2
47.11M
Shares Outstanding
freeFloat 81.42%
35.67M
13F Shares Held
▲ 889,311 vs Q2
Institutional ownership = 13F shares ÷ total outstanding. Insider % = 100 − free float. Public % = free float − institution %. Data: FMP /symbol-positions-summary + /shares-float + SEC EDGAR.
Top Institutional Holders
QTRX largest shareholders · institutional ownership
Q3 2025 · SEC 13F
Showing top 10 holders
| Holder | Shares | % Owned | Weight | Value | Reported | Change |
|---|---|---|---|---|---|---|
PORTOLAN CAPITAL MANAGEMENT, LLC laboratory analytical instruments | 4.26M | 10.95% | 10.95% | $23.13B | Nov 13, 2025 | ▲ 626.2K |
AMERIPRISE FINANCIAL INC laboratory analytical instruments | 4.24M | 10.91% | 10.91% | $23.04B | Nov 14, 2025 | ▲ 6.6K |
BLACKROCK, INC. laboratory analytical instruments | 3.11M | 8.00% | 8.00% | $16.90B | Nov 12, 2025 | ▲ 188.3K |
VANGUARD GROUP INC laboratory analytical instruments | 2.65M | 6.81% | 6.81% | $14.38B | Nov 7, 2025 | ▲ 118.6K |
INVENOMIC CAPITAL MANAGEMENT LP laboratory analytical instruments | 1.39M | 3.58% | 3.58% | $7.56B | Nov 14, 2025 | ▲ 248.1K |
WILLIAM BLAIR INVESTMENT MANAGEMENT, LLC laboratory analytical instruments | 1.32M | 3.38% | 3.38% | $7.14B | Nov 12, 2025 | ▲ 187.3K |
EASTERLY INVESTMENT PARTNERS LLC laboratory analytical instruments | 1.25M | 3.22% | 3.22% | $6.80B | Nov 12, 2025 | ▲ 168.5K |
MILLENNIUM MANAGEMENT LLC laboratory analytical instruments | 1.21M | 3.11% | 3.11% | $6.57B | Nov 14, 2025 | ▲ 1.20M |
GEODE CAPITAL MANAGEMENT, LLC laboratory analytical instruments | 1.01M | 2.60% | 2.60% | $5.50B | Nov 12, 2025 | ▲ 124.8K |
KENT LAKE PR LLC laboratory analytical instruments | 1.00M | 2.57% | 2.57% | $5.44B | Nov 14, 2025 | ▼ 1.30M |
Data from SEC Form 13F filings. Ownership bar normalised to largest holder. Change flags: isNew / isSoldOut / changeInSharesNumber (FMP extract-analytics/holder).
Institutional Activity
Q3 2025 vs prior quarter
Q3 2025
36
Increased
+4.94M shares0
New Positions
first time holders12
Decreased
−2.36M shares0
Sold Out
fully exitedNet shares change (top 50)
+2.58M
+4.94M / −2.36M
Net new holders
+24
0 new / 0 exited
Based on top 50 institutional holders by position size. Fields: isNew, isSoldOut, changeInSharesNumber (FMP extract-analytics/holder, limit=50).
Insider Buying vs Selling
QTRX insider trading · insider activity
Source: SEC Form 4
20
Buy transactions
36
Sell transactions
0.56
Buy/Sell ratio
$0M
Total disposed
Recent Insider Transactions
Showing 10 most recent · Common Stock only
| Name · Role | Date | Type | Shares | Price | Value | After Trans. | Filing |
|---|---|---|---|---|---|---|---|
Miller Michael Francis Chief Technology Officer | May 31, 2026 | Tax Withhold | 39 | $3.06 | $119.34 | 33.8K | Form 4 ↗ |
Sriram Vandana Chief Financial Officer | May 15, 2026 | Tax Withhold | 315 | $2.75 | $866.25 | 30.0K | Form 4 ↗ |
Sriram Vandana Chief Financial Officer | May 15, 2026 | Tax Withhold | 154 | $2.75 | $423.5 | 29.3K | Form 4 ↗ |
Sriram Vandana Chief Financial Officer | May 15, 2026 | Tax Withhold | 79 | $2.75 | $217.25 | 28.9K | Form 4 ↗ |
Miller Michael Francis Chief Technology Officer | May 15, 2026 | Tax Withhold | 249 | $2.75 | $684.75 | 33.7K | Form 4 ↗ |
Miller Michael Francis Chief Technology Officer | May 15, 2026 | Tax Withhold | 111 | $2.75 | $305.25 | 33.1K | Form 4 ↗ |
Miller Michael Francis Chief Technology Officer | May 15, 2026 | Tax Withhold | 41 | $2.75 | $112.75 | 32.9K | Form 4 ↗ |
Miller Michael Francis Chief Technology Officer | May 15, 2026 | Tax Withhold | 41 | $2.75 | $112.75 | 32.8K | Form 4 ↗ |
Source: /insider-trading/search (FMP stable). Buy/Sell direction: acquisitionOrDisposition A=Buy, D=Sell. RSU vesting (M-Exempt) excluded from sentiment bar. All data from SEC EDGAR public filings.
About institutional & insider ownership
Quanterix Corporation (QTRX) is primarily owned by institutional investors, who hold approximately 75.7% of total shares outstanding. Company insiders own approximately 18.58%, while retail and public investors account for the remaining 5.70%.
The largest institutional shareholder of Quanterix Corporation is PORTOLAN CAPITAL MANAGEMENT, LLC, holding approximately 4.26 million shares — equal to 10.95% of outstanding shares — as of September 30, 2025.
A total of 130 institutional investors currently hold QTRX stock, with a combined institutional value of approximately $193,729,925 as of the most recent 13F filing period.
Frequently asked questions
QTRX ownershipQuanterix Corporation (QTRX) is primarily owned by institutional investors, who hold approximately 75.7% of shares. The largest shareholder is PORTOLAN CAPITAL MANAGEMENT, LLC with a 10.95% stake. Company insiders hold 18.58%. Data sourced from SEC Form 13F as of September 30, 2025.