Overview: What qualifies as a private foundation in the US
In the US context, a private foundation is typically governed by a small set of donors, family members, or a corporation, and funded by a single major gift. Unlike public charities, they do not rely on broad public support. The largest private foundations hold multibillion-dollar endowments and operate through program staff, independent grantmaking, and often closely aligned family oversight. This guide profiles the biggest private foundations by estimated endowment size, describes their primary giving areas, and explains how they differ from larger public charities and donor-advised funds.
Why foundation size matters: assets, strategy, and impact
Foundation size affects reach, program depth, and the ability to fund long-term initiatives or take strategic risks. Larger endowments can support substantial staff, rigorous evaluation, and flexible general operating support, while smaller foundations often focus tightly on niche geographies or issue areas. Understanding a foundation’s size and structure helps grantseekers align opportunities, researchers compare funding flows, and policymakers assess philanthropic influence on public goods. This section outlines core attributes that distinguish the largest private foundations and how these attributes shape their work.
Key attributes of major US private foundations
Across the largest private foundations, common attributes include multiyear funding, emphasis on organizational capacity, and layered governance. Many operate nationally or globally, though some maintain local or regional roots. Attributes vary by mission, with education, health, and the environment among the most common focus areas. The following table provides verified, indicative attributes, assets, and giving contexts for several of the largest private foundations.
| Foundation | Assets (approx.) | Giving focus | Headquarters | Governance model | Source type |
|---|---|---|---|---|---|
| Bill & Melinda Gates Foundation | $60–70B | Global health, development, US education | Seattle, WA | Family-inflected board; CEO leadership | Reported IRS Form 990 and audited financials |
| Rockefeller Foundation | $6–7B | Equity, resilience, health, food systems | New York, NY | Trustees; president-led strategy | Audited statements; public grant listings |
| Koch Industries-related foundations (e.g., Charles Koch Foundation) | $2–3B (single largest Koch foundation estimate) | Economic freedom, governance, technology, applied sciences | Kansas/other US locations | Family board oversight | IRS 990s; foundation disclosures |
| Lilly Endowment Inc. | $30–35B | Faith-based and community development, education | Indianapolis, IN | Self-perpetuating board; CEO | IRS filings; periodic impact reports |
| Robert Wood Johnson Foundation | $13–14B | Health equity, culture of health | Princeton, NJ | Trustees; president with C-suite program teams | Audited financials; public evaluations |
| W.K. Kellogg Foundation | $10–11B | Equity, children, families, community well-being | Battle Creek, MI | Trustees; president-led strategy | IRS 990s; outcome reports |
| Andrew W. Mellon Foundation | $9–10B | Higher education, arts, conservation | New York, NY | Trustees; senior program leadership | Audited statements; grant databases |
| Gordon and Betty Moore Foundation | $9–10B | Environment, patient science, NPIs | San Francisco, CA | Foundation leadership; science-driven boards | Independent evaluations; financial disclosures |
| Walton Family Foundation | $7–8B | Education reform, conservation, community | Bentonville, AR | Family council; active board | IRS 990s; public grantmaking lists |
| Hewlett Foundation | $12–13B | Education, environment, global development | Palo Alto, CA | Trustees; collaborative program teams | Audited reports; evaluation summaries |
Differences between private foundations and public charities
Private foundations are typically funded by an individual, family, or corporation and distribute a minimum percentage of investment returns annually. Public charities, by contrast, draw support from the general public and diverse donors, which can provide broader legitimacy but may require more diversified revenue strategies. Private foundations often have more controlled governance and programmatic strategy, while public charities may engage more directly in service delivery. Understanding these structural differences is essential for prospective grantseekers and partners evaluating funding sources.
How these foundations decide where to give
Large private foundations use formal strategies, program officers, and external advisors to direct funding. Many publish searchable online grant databases and prioritize particular issue areas or geographies. Some foundations favor general operating support and multiyear commitments, while others focus on project-specific grants. Foundations may also establish collaborative initiatives, pooled funds, or challenge prizes to leverage additional resources and align multiple funders around shared goals.
Application and relationship practices
Approaching a foundation often requires researching current priorities, aligning proposals with their strategies, and submitting through indicated channels. Some foundations accept unsolicited inquiries, while others require invited submissions or letters of intent. Strong proposals typically include clear problem statements, outcomes, budgets, and, where relevant, equity considerations and stakeholder engagement. Maintaining transparent communication and reporting helps build long-term funder relationships.
Operational structure and compliance expectations
US private foundations are subject to IRS rules, including minimum distribution requirements, self-dealing prohibitions, and investment standards. Foundations must file annual information returns (Form 990-PF) and maintain proper governance documents. Larger foundations often have dedicated legal, compliance, and evaluation teams to manage these obligations. For international grantmaking, foundations may use foreign entities or intermediaries to navigate legal and logistical considerations.
Frequently asked questions (FAQs)
- How are the largest foundations ranked? Most rankings use most current audited assets from IRS filings or publicly reported financials, typically reflecting values at a point in the past several years.
- Can individuals apply to any large foundation? It depends on the foundation; many prefer invited proposals or have open calls, while others limit submissions to vetted partners or specific geographies.
- What is the difference between a private foundation and a donor-advised fund? Private foundations are distinct legal entities with independent governance; donor-advised funds are philanthropic giving tools administered by public charities, where donors receive recommendations but the sponsoring charity holds legal control.
- Are endowment figures publicly disclosed in real time? Endowments are generally reported periodically (often annually) via IRS Form 990-PF and audited financial statements; real-time values are not typically published.
- How can nonprofits find relevant foundation funding? Start by aligning mission and geography, review foundation priorities and past grantees, use foundation giving databases, and follow submission guidelines carefully.