Klaviyo IPO Presentation Deck

GAAP to Non-GAAP reconciliation (cont'd) Non-GAAP Operating Expenses (in thousands) Research and Development (R&D) Expense on a GAAP Basis Less: Amortization of Prepaid Marketing Expense Less: Stock-Based Compensation Expense ¹ Less: Restructuring Expense ² Non-GAAP R&D Expense Revenue R&D Expense as a % of Revenue Year Ended December 31 2021 $65,599 5,900 $59,699 $290,640 22.6% 2022 $104,077 1,230 $102,847 $472,748 22.0% Non-GAAP R&D Expense as a % of Revenue 20.5% ¹ Represents non-cash share-based awards granted. During the years ended December 31, 2022 and 2021, stock-based compensation expense of $1.5 million and $16.7 million, respectively, related to repurchasing and retiring our common stock which was paid in cash, and thus are excluded from the table above. 2 Represents restructuring costs incurred in connection with a reduction in the Company's workforce announced in March 2023. During the period ended March 31, 2023, stock-based compensation expense of approximately $0.5 million related to the reduction in workforce is excluded from restructuring expense and included in stock-based compensation from the table above. 21.8% Six Months Ended June 30 2022 $45,275 634 $44,641 $208,345 21.7% 21.4% 2023 Ⓒ Klaviyo 2023 $68,087 813 3,300 $63,974 $320,674 21.2% 19.9% Confidential 51

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