Company: BLLN
Filing Date: 2025-08-11
Form Type: DRS/A
Source: 0000950123-25-007483
Chunk: 29

Company: BillionToOne, Inc.
Filing Date: 2025-08-11
Form: DRS/A
Chunk 29
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| Risk factors | See the section titled “Risk factors” for a discussion of factors that you should consider carefully before deciding to invest in our Class A common stock. |

| Proposed Nasdaq Global Market trading symbol | “BLLN” |

The number of shares of our common stock to be outstanding after this offering is based on shares of our Class A common stock and shares of our Class B common stock outstanding as of June 30, 2025, after giving effect to the Preferred Stock Conversion, the Reclassification and the Class B Stock Exchange (each as defined below), in each case as if they had occurred on June 30, 2025, and excludes:

| • |     | up to 9,660 shares of our Class A common stock issuable upon the exercise of a redeemable convertible preferred stock 
 warrant (the A-6 Warrant) for an exercise price of $2.5879 per share;                                                 |

| • |     | up to 80,357 shares of our Class A common stock issuable upon the exercise of a 2021 common stock warrant (the 2021 
 Common Warrant) for an exercise price of $2.80 per share;                                                           |

| • |     | up to 41,209 shares of our Class A common stock issuable upon the exercise of a 2022 common stock warrant (the 2022 
 Common Warrant) for an exercise price of $10.92 per share;                                                          |

| • |     | shares of our Class A common stock reserved for future issuance under our 2025 Equity Incentive                                                                                                                                                
 Plan (the 2025 Plan), which will become effective upon the effectiveness of the registration statement of which this prospectus forms a part, as well as any future increases in the number of shares of our Class A common stock reserved for 
 issuance under the 2025 Plan; and                                                                                                                                                                                                              |

| • |     | shares of our Class A common stock reserved for future issuance under our 2025 Employee Stock                                                                                                                                                  
 Purchase Plan (ESPP), which will become effective upon the effectiveness of the registration statement of which this prospectus forms a part, as well as any future increases in the number of shares of our Class A common stock reserved for 
 issuance under the ESPP.                                                                                                                                                                                                                       |

Unless otherwise indicated, this prospectus reflects and assumes the following:

| • |     | the automatic conversion of all    outstanding shares of our redeemable convertible preferred stock