Company: BLLN
Filing Date: 2025-10-17
Form Type: S-1/A
Source: 0001193125-25-242632
Chunk: 134

Company: BillionToOne, Inc.
Filing Date: 2025-10-17
Form: S-1/A
Chunk 134
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     | $                   |  221,228 |   |     | $         |  221,479 |   |     | $              |  401,872 |   |

85

| (1) |     | Each $1.00 increase or decrease in the assumed initial public offering price of $52.00 per share, the midpoint of the estimated offering price range set forth on the cover page of this prospectus, would increase or                           
 decrease, as applicable, pro forma as adjusted cash and cash equivalents, additional paid-in capital, total stockholders’ (deficit) equity and total capitalization by approximately $3.6 million,                                               
 assuming that the number of shares offered by us, as set forth on the cover page of this prospectus, remains the same, and after deducting underwriting discounts and commissions and estimated offering expenses payable by us. Similarly, each 
 1.0 million share increase or decrease in the number of shares offered by us would increase or decrease, as applicable, pro forma as adjusted cash and cash equivalents, additional paid-in capital, total                                       
 stockholders’ (deficit) equity and total capitalization by approximately $48.4 million, assuming that the assumed initial offering price to the public remains the same, and after deducting underwriting discounts and commissions and          
 estimated offering expenses payable by us.                                                                                                                                                                                                       |

The number of shares of our common stock issued and outstanding after this offering in the table above is based on 39,462,629 shares of our Class A common stock and 4,552,650 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, in each case as if they had occurred on June 30, 2025, and excludes:

| • |     | 8,930,919 shares of our Class A common stock issuable upon the exercise of stock options outstanding as of 
 June 30, 2025 under our 2018 Plan, at a weighted-average exercise price of $10.59 per share;               |

| • |     | 1,224,549 shares of our Class A common stock issuable upon the exercise of outstanding stock options that were granted 
 subsequent to June 30, 2025 under our 2018 Plan, at a weighted-average exercise price of $28.88 per share;             |

| • |     | up to 9,