Company: BLLN
Filing Date: 2025-10-07
Form Type: S-1
Source: 0001193125-25-233697
Chunk: 290

Company: BillionToOne, Inc.
Filing Date: 2025-10-07
Form: S-1
Chunk 290
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 entities identified in this table have sole voting and investment power with respect to all shares shown as beneficially owned by them, subject to applicable community property laws. The percentage ownership information shown in the table prior to this offering is based upon 35,680,833 shares of Class A common stock and 4,552,650 shares of Class B common stock outstanding as of September 30, 2025, assuming (i) the Preferred Stock Conversion, (ii) the Reclassification, and (iii) the Class B Stock Exchange. The percentage ownership information shown in the table after this offering is based upon shares of Class A common stock and 4,552,650 shares of Class B common stock outstanding immediately after the closing of the offering, assuming no exercise of the underwriters’ option to purchase additional shares of Class A common stock. We have deemed shares of our Class A common stock subject to stock options that are currently exercisable or exercisable within 60 days of September 30, 2025 to be outstanding and to be beneficially owned by the person holding the stock option for the purpose of computing the percentage ownership of that person. We did not deem these shares outstanding, however, for the purpose of computing the percentage ownership of any other person. In addition, the table below excludes any potential purchases in this offering by the beneficial owners identified in the table below, including in the directed share program. Except as otherwise noted below, the address for persons listed in the table is c/o BillionToOne, Inc., 1035 O’Brien Drive, Menlo Park, CA 94025. 219

|                                                                         |     | Class A       
 shares        
 beneficially  
 owned before  
 this offering |            |     |   |      |     | Class B shares       
 beneficially owned   
 before this offering |           |     |   |       |     | % total  
 voting   
 power    
 before   
 this     
 offering |       |     | Class A       
 shares        
 beneficially  
 owned         
 after         
 this offering |     |   |     | Class B      
 shares       
 beneficially 
 owned after  
 this         
 offering     |     |   |     | % total  
 voting   
 power    
 after    
 this     
 offering |
| Name of beneficial                                                      
 owner                                                                   |     | Number        |            |     | % |      |     | Number               |           |     | % |       |     |          |       |     | Number        |     | % |     | Number       |     | % |     | %