TSP C Fund Passes $500 Billion: What You Actually Own

Last Updated: June 28, 2026 Reading Time: 7 min

The TSP C Fund just crossed $500 billion for the first time. As of May 31, 2026, it held $507.9 billion and made up 43.9% of the entire $1.156 trillion plan. That milestone is a sign of a healthy plan, but it's also a good moment to look at what's actually inside the most popular fund federal employees own, because a third of it now sits in about seven companies.

Key Takeaways

  • The C Fund hit $507.9 billion in May 2026, including its share inside the L funds, and is now 43.9% of all TSP assets.
  • Total TSP assets set a record of $1.156 trillion the same month. The I Fund crossed $150 billion and the L funds together passed $300 billion.
  • The C Fund tracks the S&P 500, where the top 10 stocks are roughly 38-40% of the index and the Magnificent 7 are about 32.7%.
  • In 2026 so far, the S Fund (+16.3%) and I Fund (+15.2%) are both beating the C Fund (+8.1%).
  • This is education on what the data shows, not investment advice. FedTools is not a licensed advisor.

The Milestone, in Plain Numbers

The $507.9 billion figure comes from data presented at the Federal Retirement Thrift Investment Board (FRTIB) monthly board meeting and reported by FedWeek on June 23, 2026.

One clarification worth making: that number includes the C Fund shares held inside the lifecycle (L) funds, which invest part of their money in the C Fund. So $507.9 billion is the total economic footprint of the C Fund across every account type, not just the balances of people who explicitly picked the C Fund.

Milestone Date C Fund assets Share of TSP
Total TSP hits $1 trillion June 20, 2025 ~$380B (est.) ~38%
C Fund alone hits $500 billion May 2026 $507.9B 43.9%

The C Fund has been the plan's center of gravity for a long time. What's new is the sheer scale, and what that scale now represents under the hood.

What's Actually Inside the C Fund

The C Fund mirrors the S&P 500 index, weighted by each company's market value. That weighting is the part most federal employees don't think about. As of mid-June 2026:

  • The top 10 stocks are roughly 38-40% of the entire index.
  • The Magnificent 7 (Nvidia, Apple, Microsoft, Amazon, Alphabet, Meta, Tesla) are about 32.7%.
  • The top 3 alone (Nvidia ~7%, Apple ~6.3%, Microsoft ~4.6%) are about 18%.

Put in dollar terms, using those index weights against $507.9 billion, roughly $35.6 billion of C Fund money tracks Nvidia alone, about $32 billion tracks Apple, and the top seven names together represent around $166 billion. That's rough multiplication based on index weights, not a direct holdings disclosure, but it makes the point: a federal employee with 100% in the C Fund has about a third of their domestic stock exposure riding on seven companies.

This isn't a brand-new risk. The C Fund has held all 500 stocks in market-cap proportion since it launched in 1988. The concentration is just more visible now that a handful of megacaps have grown so large.

C Fund vs S Fund vs I Fund: The 2026 Scoreboard

The C Fund's long-term record is strong: +26.25% in 2023, +24.96% in 2024, and +17.85% in 2025. Since inception in January 1988, it has compounded at about 11.4% a year.

But 2026 so far tells a different story, with the other stock funds out front.

Fund Tracks YTD 2026 2025 2024 2023
C Fund S&P 500 +8.1% +17.85% +24.96% +26.25%
S Fund U.S. small/mid cap +16.3% +11.38% +16.93% +26.87%
I Fund International developed +15.2% +32.45% +4.27% +17.27%
G Fund U.S. Treasuries +2.1% +4.44% +4.40% +3.87%
F Fund U.S. bonds +1.1% +7.21% +1.33% +5.53%

Returns through late June 2026 (tspfolio.com); annual figures from FRTIB/FedSmith recaps. Past performance does not predict future returns.

One year doesn't make a trend. The C Fund beat both the S and I funds in 2024. The takeaway isn't "switch," it's that spreading equity money across C, S, and I gives you exposure beyond the megacaps that now dominate the S&P 500. The L funds do that spreading automatically and rebalance daily.

Model Your Own TSP Allocation

Before you change anything, see how different mixes compound over your remaining years of service. Use our free TSP Growth & Withdrawal Calculator to compare a C-only balance against a C/S/I split and project your retirement number. Run your TSP scenario.

Frequently Asked Questions

What percentage of the TSP is in the C Fund?

As of May 31, 2026, the C Fund represents 43.9% of all TSP assets, including its share held inside the L funds. In direct participant allocation terms, federal employees had put about 35% of their balances into the C Fund as of December 2025, making it the single largest fund in the plan.

Is the C Fund too concentrated in a few big tech stocks?

It's a fair question. The C Fund holds all 500 S&P 500 stocks, but the index is weighted by market value. As of mid-2026, the top 10 stocks are about 38-40% of the index and the Magnificent 7 are roughly 32.7%. So a 100% C Fund balance puts about a third of your domestic stock exposure in seven companies. That's education, not advice.

Should I move from the C Fund to the S or I Fund?

That's a personal decision based on your timeline and risk tolerance. What the data shows in 2026: the S Fund (+16.3% YTD) and I Fund (+15.2% YTD) are both well ahead of the C Fund (+8.1% YTD). The L funds spread money across C, S, and I automatically. FedTools is not a licensed advisor, so use the TSP calculator to model your own scenarios.

Does the C Fund's size affect its returns?

No. The C Fund is a passive index fund that holds the S&P 500 in proportion to each stock's weight. Size doesn't drag on a passive fund the way it can for an active manager. The fund's expense ratio is just 0.025%, among the lowest of any retirement plan.