WHITE MOUNTAINS INSURANCE GROUP LTD

This report includes eleven non-GAAP financial measures that have been reconciled from their most comparable GAAP financial measures.

Ark’s tangible book value, growth in tangible book value and tangible capital

Ark’s tangible book value, growth in tangible book value and tangible capital are non-GAAP financial measures. Tangible book value is a non-GAAP financial measure derived by adjusting GAAP book value to exclude (i) goodwill and other intangible assets, (ii) the deferred tax liability on other intangible assets and (iii) the contingent consideration liability. The contingent consideration liability represents the estimated fair value of the additional shares that could be earned by management rollover shareholders if and to the extent that White Mountains achieves certain MOIC return thresholds. If earned, these additional shares would result in a reallocation of economics among Ark’s shareholders, which is reflected in the fair value of the contingent consideration liability recorded by White Mountains, but would have no impact on Ark’s stand-alone book value or tangible book value. Growth in tangible book value equals the change in tangible book value plus dividends for the period divided by beginning tangible book value. Ark’s tangible capital is a non-GAAP financial measure derived by adding debt to tangible book value. White Mountains believes that these non-GAAP financial measures are useful to management and investors in evaluating Ark’s enterprise value.

The following table presents the reconciliation of Ark’s GAAP book value to tangible book value and tangible capital:

(1) Amounts are net of deferred tax liabilities related to other intangible assets of $43.9.

Kudu’s EBITDA and adjusted EBITDA

Kudu's EBITDA and adjusted EBITDA are non-GAAP financial measures. EBITDA is a non-GAAP financial measure that adds back interest expense on debt, income tax (expense) benefit, depreciation and amortization of other intangible assets to GAAP net income (loss). Adjusted EBITDA is a non-GAAP financial measure that excludes certain other items in GAAP net income (loss) in addition to those added back to calculate EBITDA. The items relate to (i) net realized and unrealized investment gains (losses) on Kudu's Participation Contracts and (ii) transaction expenses. A description of each item follows:

•Net realized and unrealized investment gains (losses) - Represents net unrealized investment gains and losses recorded on Kudu’s Participation Contracts, which are recorded at fair value under GAAP, and realized investment gains and losses on Kudu’s Participation Contracts sold during the period.

•Transaction expenses - Represents costs directly related to Kudu’s mergers and acquisitions activity, such as external lawyer, banker, consulting and placement agent fees, which are not capitalized and are expensed under GAAP.

White Mountains believes that these non-GAAP financial measures are useful to management and investors in evaluating Kudu’s underlying performance. See page 68 for the reconciliation of Kudu’s GAAP net income (loss) to EBITDA and adjusted EBITDA.

Distinguished’s ScaleCo net income (loss), ScaleCo EBITDA and ScaleCo adjusted EBITDA

Distinguished’s ScaleCo net income (loss), ScaleCo EBITDA and ScaleCo adjusted EBITDA are non-GAAP financial measures. ScaleCo net income (loss) is a non-GAAP financial measure that excludes the results of the GrowthCo vertical, which is consolidated under GAAP, from Distinguished’s consolidated GAAP net income (loss). ScaleCo EBITDA is a non-GAAP financial measure that adds back interest expense on debt, income tax (expense) benefit, depreciation and amortization of other intangible assets to ScaleCo net income (loss). ScaleCo adjusted EBITDA is a non-GAAP financial measure that excludes certain other items in GAAP net income (loss) in addition to those items added back to calculate ScaleCo EBITDA. The items relate to (i) non-cash equity-based compensation expense, (ii) restructuring expenses and (iii) legal settlement expenses. A description of each item follows:

•Non-cash equity-based compensation expense - Represents non-cash expenses related to Distinguished’s management compensation that are settled with equity units in Distinguished.

•Restructuring expenses - Represents costs related to Distinguished’s corporate restructuring and capital planning activities.

•Legal settlement expenses -Represents amounts incurred related to legal settlements.

White Mountains believes that these non-GAAP financial measures are useful to management and investors in evaluating Distinguished’s underlying performance. White Mountains also believes that excluding the results of the GrowthCo vertical, which Distinguished views as an investment in start-up programs, is useful to understanding the underlying performance of Distinguished’s established programs. See page 74 for the reconciliation of Distinguished’s consolidated GAAP net income (loss) to ScaleCo net income (loss), ScaleCo EBITDA and ScaleCo adjusted EBITDA.

WTM Partners’s EBITDA and adjusted EBITDA

WTM Partners’s EBITDA and adjusted EBITDA are non-GAAP financial measures. EBITDA is a non-GAAP financial measure that adds back interest expense on debt, income tax (expense) benefit, depreciation and amortization of other intangible assets to GAAP net income (loss). Adjusted EBITDA is a non-GAAP financial measure that excludes certain other items in GAAP net income (loss) in addition to those added back to calculate EBITDA. The items relate to (i) transaction expenses and (ii) restructuring and integration expenses. A description of each item follows:

•Transaction expenses - Represents costs directly related to WTM Partners’s mergers and acquisitions activity, such as external lawyer, banker, consulting and placement agent fees, which are not capitalized and are expensed under GAAP.

•Restructuring and integration expenses - Represents costs related to WTM Partners’s corporate restructuring and mergers and acquisitions integration activities.

White Mountains believes that these non-GAAP financial measures are useful to management and investors in evaluating WTM Partners’s underlying performance. See page 76 for the reconciliation of WTM Partners’s GAAP net income (loss) to EBITDA and adjusted EBITDA.

Total consolidated portfolio return excluding MediaAlpha

Total consolidated portfolio return excluding MediaAlpha is a non-GAAP financial measure that removes the net investment income and net realized and unrealized investment gains (losses) from White Mountains’s investment in MediaAlpha. White Mountains believes this measure to be useful to management and investors by showing the underlying performance of White Mountains’s investment portfolio without regard to White Mountains’s investment in MediaAlpha.

The following table presents return reconciliations from GAAP to the reported percentages for the three and six months ended June 30, 2026 and 2025: